powerpc: Force inlining of cpu_has_feature() to avoid build failure

The code relies on constant folding of cpu_has_feature() based
on possible and always true values as defined per
CPU_FTRS_ALWAYS and CPU_FTRS_POSSIBLE.

Build failure is encountered with for instance
book3e_all_defconfig on kisskb in the AMDGPU driver which uses
cpu_has_feature(CPU_FTR_VSX_COMP) to decide whether calling
kernel_enable_vsx() or not.

The failure is due to cpu_has_feature() not being inlined with
that configuration with gcc 4.9.

In the same way as commit acdad8fb ("powerpc: Force inlining of
mmu_has_feature to fix build failure"), for inlining of
cpu_has_feature().
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/b231dfa040ce4cc37f702f5c3a595fdeabfe0462.1615378209.git.christophe.leroy@csgroup.eu

arch/powerpc/include/asm/cpu_has_feature.h

@@ -7,7 +7,7 @@
 #include <linux/bug.h>
 #include <asm/cputable.h>
 
-static inline bool early_cpu_has_feature(unsigned long feature)
+static __always_inline bool early_cpu_has_feature(unsigned long feature)
 {
 	return !!((CPU_FTRS_ALWAYS & feature) ||
 		  (CPU_FTRS_POSSIBLE & cur_cpu_spec->cpu_features & feature));
@@ -46,7 +46,7 @@ static __always_inline bool cpu_has_feature(unsigned long feature)
 	return static_branch_likely(&cpu_feature_keys[i]);
 }
 #else
-static inline bool cpu_has_feature(unsigned long feature)
+static __always_inline bool cpu_has_feature(unsigned long feature)
 {
 	return early_cpu_has_feature(feature);
 }