compiler_attributes.h: drop __has_attribute() support for gcc4

Now that GCC 5.1 is the minimally supported default, the manual
workaround for older gcc versions not having __has_attribute() are no
longer relevant and can be removed.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/compiler_attributes.h

@@ -20,26 +20,6 @@
  * Provide links to the documentation of each supported compiler, if it exists.
  */
 
-/*
- * __has_attribute is supported on gcc >= 5, clang >= 2.9 and icc >= 17.
- * In the meantime, to support gcc < 5, we implement __has_attribute
- * by hand.
- */
-#ifndef __has_attribute
-# define __has_attribute(x) __GCC4_has_attribute_##x
-# define __GCC4_has_attribute___assume_aligned__      1
-# define __GCC4_has_attribute___copy__                0
-# define __GCC4_has_attribute___designated_init__     0
-# define __GCC4_has_attribute___externally_visible__  1
-# define __GCC4_has_attribute___no_caller_saved_registers__ 0
-# define __GCC4_has_attribute___noclone__             1
-# define __GCC4_has_attribute___no_profile_instrument_function__ 0
-# define __GCC4_has_attribute___nonstring__           0
-# define __GCC4_has_attribute___no_sanitize_address__ 1
-# define __GCC4_has_attribute___no_sanitize_undefined__ 1
-# define __GCC4_has_attribute___fallthrough__         0
-#endif
-
 /*
  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alias-function-attribute
  */