powerpc/sstep: Fix DS operand in ld encoding to appropriate value

ld instruction should have 14 bit immediate field (DS) concatenated
with 0b00 on the right, encode it accordingly. Introduce macro
`IMM_DS()` to encode DS form instructions with 14 bit immediate field.

Fixes: 4ceae137bd ("powerpc: emulate_step() tests for load/store instructions")
Reviewed-by: Sandipan Das <sandipan@linux.ibm.com>
Signed-off-by: Balamuruhan S <bala24@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200311102405.392263-1-bala24@linux.ibm.com

arch/powerpc/lib/test_emulate_step.c

@@ -13,19 +13,20 @@
 #include <asm/code-patching.h>
 
 #define IMM_L(i)		((uintptr_t)(i) & 0xffff)
+#define IMM_DS(i)		((uintptr_t)(i) & 0xfffc)
 
 /*
  * Defined with TEST_ prefix so it does not conflict with other
  * definitions.
  */
 #define TEST_LD(r, base, i)	(PPC_INST_LD | ___PPC_RT(r) |		\
-					___PPC_RA(base) | IMM_L(i))
+					___PPC_RA(base) | IMM_DS(i))
 #define TEST_LWZ(r, base, i)	(PPC_INST_LWZ | ___PPC_RT(r) |		\
 					___PPC_RA(base) | IMM_L(i))
 #define TEST_LWZX(t, a, b)	(PPC_INST_LWZX | ___PPC_RT(t) |		\
 					___PPC_RA(a) | ___PPC_RB(b))
 #define TEST_STD(r, base, i)	(PPC_INST_STD | ___PPC_RS(r) |		\
-					___PPC_RA(base) | ((i) & 0xfffc))
+					___PPC_RA(base) | IMM_DS(i))
 #define TEST_LDARX(t, a, b, eh)	(PPC_INST_LDARX | ___PPC_RT(t) |	\
 					___PPC_RA(a) | ___PPC_RB(b) |	\
 					__PPC_EH(eh))