MIPS: remove GCC < 4.9 support

Remove a tautology; since
commit 0bddd227f3dc ("Documentation: update for gcc 4.9 requirement")
which raised the minimally supported version of GCC to 4.9, this case is
always true.

Link: https://github.com/ClangBuiltLinux/linux/issues/427
Signed-off-by: Nick Desaulniers <[e-mail]>
Signed-off-by: Thomas Bogendoerfer <[e-mail]>

arch/mips/include/asm/compiler.h

···
 #undef barrier_before_unreachable
 #define barrier_before_unreachable() asm volatile(".insn")
 
-#if !defined(CONFIG_CC_IS_GCC) || \
-    (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)
-# define GCC_OFF_SMALL_ASM() "ZC"
-#elif defined(CONFIG_CPU_MICROMIPS)
-# error "microMIPS compilation unsupported with GCC older than 4.9"
-#else
-# define GCC_OFF_SMALL_ASM() "R"
-#endif
+#define GCC_OFF_SMALL_ASM() "ZC"
 
 #ifdef CONFIG_CPU_MIPSR6
 #define MIPS_ISA_LEVEL "mips64r6"