x86/elf: Use _BITUL() macro in UAPI headers

Replace BIT() in x86's UAPI header with _BITUL(). BIT() is not defined
in the UAPI headers and its usage may cause userspace build errors.

Fixes: 742c45c3 ("x86/elf: Enumerate kernel FSGSBASE capability in AT_HWCAP2")
Signed-off-by: Joe Richey <joerichey@google.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210521085849.37676-2-joerichey94@gmail.com

arch/x86/include/uapi/asm/hwcap2.h

@@ -2,10 +2,12 @@
 #ifndef _ASM_X86_HWCAP2_H
 #define _ASM_X86_HWCAP2_H
 
+#include <linux/const.h>
+
 /* MONITOR/MWAIT enabled in Ring 3 */
-#define HWCAP2_RING3MWAIT		(1 << 0)
+#define HWCAP2_RING3MWAIT		_BITUL(0)
 
 /* Kernel allows FSGSBASE instructions available in Ring 3 */
-#define HWCAP2_FSGSBASE			BIT(1)
+#define HWCAP2_FSGSBASE			_BITUL(1)
 
 #endif