x86/sev: Fix nonistr violation

When the compiler fails to inline, it violates nonisntr:

  vmlinux.o: warning: objtool: __sev_es_nmi_complete()+0xc7: call to sev_es_wr_ghcb_msr() leaves .noinstr.text section

Fixes: 4ca68e02 ("x86/sev-es: Handle NMI State")
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210106144017.532902065@infradead.org

arch/x86/kernel/sev-es.c

@@ -225,7 +225,7 @@ static inline u64 sev_es_rd_ghcb_msr(void)
 	return __rdmsr(MSR_AMD64_SEV_ES_GHCB);
 }
 
-static inline void sev_es_wr_ghcb_msr(u64 val)
+static __always_inline void sev_es_wr_ghcb_msr(u64 val)
 {
 	u32 low, high;