selftests/powerpc: Don't save TOC by default in asm helpers

Thare are some asm helpers for creating/popping stack frames in
basic_asm.h. They always save/restore r2 (TOC pointer), but none of the
selftests change r2, so it's unnecessary to save it by default.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220627140239.2464900-5-mpe@ellerman.id.au

tools/testing/selftests/powerpc/include/basic_asm.h

@@ -58,11 +58,9 @@
 #define PUSH_BASIC_STACK(_extra) \
 	mflr	r0; \
 	std	r0, STACK_FRAME_LR_POS(%r1); \
-	stdu	%r1, -(((_extra + 15) & ~15) + STACK_FRAME_MIN_SIZE)(%r1); \
-	std	%r2, STACK_FRAME_TOC_POS(%r1);
+	stdu	%r1, -(((_extra + 15) & ~15) + STACK_FRAME_MIN_SIZE)(%r1);
 
 #define POP_BASIC_STACK(_extra) \
-	ld	%r2, STACK_FRAME_TOC_POS(%r1); \
 	addi	%r1, %r1, (((_extra + 15) & ~15) + STACK_FRAME_MIN_SIZE); \
 	ld	r0, STACK_FRAME_LR_POS(%r1); \
 	mtlr	r0;