mips: Remove compiler check in unroll macro

CONFIG_CC_IS_GCC is undefined when Clang is used, which breaks the build
(see our Travis link below).

Clang 8 was chosen as a minimum version for this check because there
were some improvements around __builtin_constant_p in that release. In
reality, MIPS was not even buildable until clang 9 so that check was not
technically necessary. Just remove all compiler checks and just assume
that we have a working compiler.

Fixes: d4e60453 ("Restore gcc check in mips asm/unroll.h")
Link: https://travis-ci.com/github/ClangBuiltLinux/continuous-integration/jobs/359642821Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/mips/include/asm/unroll.h

@@ -25,9 +25,7 @@
 	 * generate reasonable code for the switch statement,	\
 	 * so we skip the sanity check for those compilers.	\
 	 */							\
-	BUILD_BUG_ON((CONFIG_CC_IS_GCC ||			\
-		      CONFIG_CLANG_VERSION >= 80000) &&		\
-		     !__builtin_constant_p(times));		\
+	BUILD_BUG_ON(!__builtin_constant_p(times));		\
 								\
 	switch (times) {					\
 	case 32: fn(__VA_ARGS__); /* fall through */		\