arm64: Drop workaround for broken 'S' constraint with GCC 4.9

Since GCC < 5.1 has been shown to be unsuitable for the arm64 kernel,
let's drop the workaround for the 'S' asm constraint that GCC 4.9
doesn't always grok.

This is effectively a revert of 9fd339a4 ("arm64: Work around
broken GCC 4.9 handling of "S" constraint").
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210118130129.2875949-1-maz@kernel.orgSigned-off-by: Will Deacon <will@kernel.org>

arch/arm64/include/asm/kvm_asm.h

@@ -199,12 +199,6 @@ extern void __vgic_v3_init_lrs(void);
 
 extern u32 __kvm_get_mdcr_el2(void);
 
-#if defined(GCC_VERSION) && GCC_VERSION < 50000
-#define SYM_CONSTRAINT	"i"
-#else
-#define SYM_CONSTRAINT	"S"
-#endif
-
 /*
  * Obtain the PC-relative address of a kernel symbol
  * s: symbol
@@ -221,7 +215,7 @@ extern u32 __kvm_get_mdcr_el2(void);
 		typeof(s) *addr;					\
 		asm("adrp	%0, %1\n"				\
 		    "add	%0, %0, :lo12:%1\n"			\
-		    : "=r" (addr) : SYM_CONSTRAINT (&s));		\
+		    : "=r" (addr) : "S" (&s));				\
 		addr;							\
 	})