powerpc/perf: Drop MMCRA from thread_struct

In commit 59affcd3 "Context switch more PMU related SPRs" I added more
PMU SPRs to thread_struct, later modified in commit b11ae95. To add
insult to injury it turns out we don't need to switch MMCRA as it's
only user readable, and the value is recomputed by the PMU code.
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/asm/processor.h

@@ -289,7 +289,6 @@ struct thread_struct {
 	unsigned long	sier;
 	unsigned long	mmcr0;
 	unsigned long	mmcr2;
-	unsigned long	mmcra;
 #endif
 };
 

arch/powerpc/kernel/asm-offsets.c

@@ -132,7 +132,6 @@ int main(void)
 	DEFINE(THREAD_SIER, offsetof(struct thread_struct, sier));
 	DEFINE(THREAD_MMCR0, offsetof(struct thread_struct, mmcr0));
 	DEFINE(THREAD_MMCR2, offsetof(struct thread_struct, mmcr2));
-	DEFINE(THREAD_MMCRA, offsetof(struct thread_struct, mmcra));
 #endif
 #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
 	DEFINE(PACATMSCRATCH, offsetof(struct paca_struct, tm_scratch));