powerpc: Prepare for splitting giveup_{fpu, altivec, vsx} in two

This prepares for the decoupling of saving {fpu,altivec,vsx} registers and
marking {fpu,altivec,vsx} as being unused by a thread.

Currently giveup_{fpu,altivec,vsx}() does both however optimisations to
task switching can be made if these two operations are decoupled.
save_all() will permit the saving of registers to thread structs and leave
threads MSR with bits enabled.

This patch introduces no functional change.

Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/reg.h

@@ -75,6 +75,14 @@
 #define MSR_HV		0
 #endif
 
+/*
+ * To be used in shared book E/book S, this avoids needing to worry about
+ * book S/book E in shared code
+ */
+#ifndef MSR_SPE
+#define MSR_SPE 	0
+#endif
+
 #define MSR_VEC		__MASK(MSR_VEC_LG)	/* Enable AltiVec */
 #define MSR_VSX		__MASK(MSR_VSX_LG)	/* Enable VSX */
 #define MSR_POW		__MASK(MSR_POW_LG)	/* Enable Power Management */