powerpc/64e: Fix build failure with GCC 12 (unrecognized opcode: `wrteei')

With GCC 12, corenet64_smp_defconfig leads to the following build errors:

  CC      arch/powerpc/kernel/irq.o
{standard input}: Assembler messages:
{standard input}:3616: Error: unrecognized opcode: `wrteei'
{standard input}:5689: Error: unrecognized opcode: `wrteei'
  CC      arch/powerpc/kernel/pmc.o
{standard input}: Assembler messages:
{standard input}:42: Error: unrecognized opcode: `mfpmr'
{standard input}:53: Error: unrecognized opcode: `mtpmr'
  CC      arch/powerpc/kernel/io.o
{standard input}: Assembler messages:
{standard input}:376: Error: unrecognized opcode: `mbar'
...
  CC      arch/powerpc/mm/nohash/book3e_hugetlbpage.o
{standard input}: Assembler messages:
{standard input}:291: Error: unrecognized opcode: `tlbsx'
{standard input}:482: Error: unrecognized opcode: `tlbwe'
{standard input}:608: Error: unrecognized opcode: `lbarx'
{standard input}:608: Error: unrecognized opcode: `stbcx.'

-mpcu=powerpc64 cannot be used anymore for book3e, it must be a booke CPU.

But then we get:

  CC      arch/powerpc/lib/xor_vmx.o
cc1: error: AltiVec not supported in this target

Altivec is not supported with -mcpu=e5500 so don't allow selection
of altivec when e5500 is selected.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/77255a5a957967723b84d0356d9e5fb21569f4e8.1657549153.git.christophe.leroy@csgroup.eu

arch/powerpc/Makefile

@@ -168,13 +168,7 @@ endif
 CFLAGS-$(CONFIG_TARGET_CPU_BOOL) += $(call cc-option,-mcpu=$(CONFIG_TARGET_CPU))
 AFLAGS-$(CONFIG_TARGET_CPU_BOOL) += $(call cc-option,-mcpu=$(CONFIG_TARGET_CPU))
 
-# Altivec option not allowed with e500mc64 in GCC.
-ifdef CONFIG_ALTIVEC
-E5500_CPU := -mcpu=powerpc64
-else
-E5500_CPU := $(call cc-option,-mcpu=e500mc64,-mcpu=powerpc64)
-endif
-CFLAGS-$(CONFIG_E5500_CPU) += $(E5500_CPU)
+CFLAGS-$(CONFIG_E5500_CPU) += $(call cc-option,-mcpu=e500mc64,-mcpu=powerpc64)
 CFLAGS-$(CONFIG_E6500_CPU) += $(call cc-option,-mcpu=e6500,$(E5500_CPU))
 
 asinstr := $(call as-instr,lis 9$(comma)foo@high,-DHAVE_AS_ATHIGH=1)

arch/powerpc/platforms/Kconfig.cputype

@@ -126,12 +126,12 @@ choice
 
 config GENERIC_CPU
 	bool "Generic (POWER4 and above)"
-	depends on PPC64 && !CPU_LITTLE_ENDIAN
-	select PPC_64S_HASH_MMU if PPC_BOOK3S_64
+	depends on PPC_BOOK3S_64 && !CPU_LITTLE_ENDIAN
+	select PPC_64S_HASH_MMU
 
 config GENERIC_CPU
 	bool "Generic (POWER8 and above)"
-	depends on PPC64 && CPU_LITTLE_ENDIAN
+	depends on PPC_BOOK3S_64 && CPU_LITTLE_ENDIAN
 	select ARCH_HAS_FAST_MULTIPLIER
 	select PPC_64S_HASH_MMU
 
@@ -358,7 +358,7 @@ config PHYS_64BIT
 
 config ALTIVEC
 	bool "AltiVec Support"
-	depends on PPC_BOOK3S_32 || PPC_BOOK3S_64 || (PPC_E500MC && PPC64)
+	depends on PPC_BOOK3S || (PPC_E500MC && PPC64 && !E5500_CPU)
 	select PPC_FPU
 	help
 	  This option enables kernel support for the Altivec extensions to the