time: Introduce CONFIG_COMPAT_32BIT_TIME

Compat functions are now used to support 32 bit time_t in
compat mode on 64 bit architectures and in native mode on
32 bit architectures.

Introduce COMPAT_32BIT_TIME to conditionally compile these
functions.

Note that turning off 32 bit time_t support requires more
changes on architecture side. For instance, architecure
syscall tables need to be updated to drop support for 32 bit
time_t syscalls.

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/Kconfig

@@ -878,6 +878,13 @@ config 64BIT_TIME
 	  architectures, and 64-bit architectures as part of compat syscall
 	  handling.
 
+config COMPAT_32BIT_TIME
+	def_bool (!64BIT && 64BIT_TIME) || COMPAT
+	help
+	  This enables 32 bit time_t support in addition to 64 bit time_t support.
+	  This is relevant on all 32-bit architectures, and 64-bit architectures
+	  as part of compat syscall handling.
+
 config ARCH_NO_COHERENT_DMA_MMAP
 	bool