include/linux/compiler-gcc.h: sparse can do constant folding of __builtin_bswap*()

Sparse can do constant folding of __builtin_bswap*() since 2017.  Also, a
much recent version of Sparse is needed anyway, see commit 6ec4476ac8
("Raise gcc version requirement to 4.9").

So, remove the comment about sparse not being yet able to constant fold
__builtin_bswap*() and remove the corresponding test of __CHECKER__.

Link: https://lkml.kernel.org/r/20210226092236.99369-1-luc.vanoostenryck@gmail.com
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/compiler-gcc.h

@@ -90,15 +90,11 @@
  */
 #define asm_volatile_goto(x...)	do { asm goto(x); asm (""); } while (0)
 
-/*
+#if defined(CONFIG_ARCH_USE_BUILTIN_BSWAP)
- * sparse (__CHECKER__) pretends to be gcc, but can't do constant
- * folding in __builtin_bswap*() (yet), so don't set these for it.
- */
-#if defined(CONFIG_ARCH_USE_BUILTIN_BSWAP) && !defined(__CHECKER__)
 #define __HAVE_BUILTIN_BSWAP32__
 #define __HAVE_BUILTIN_BSWAP64__
 #define __HAVE_BUILTIN_BSWAP16__
-#endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP && !__CHECKER__ */
+#endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP */
 
 #if GCC_VERSION >= 70000
 #define KASAN_ABI_VERSION 5