Revert "lib: Emit nop,no5 instructions combo for x86_64 arch"

This reverts commit c9865d1.

Currently kernel implementation of this optimization can corrupt red zone and
corrupt application. Until this is figured out in the kernel, avoid emitting
nop+nop5 sequence.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

Author: anakryiko

usdt.h

@@ -312,8 +312,6 @@ struct usdt_sema { volatile unsigned short active; };
 #ifndef USDT_NOP
 #if defined(__ia64__) || defined(__s390__) || defined(__s390x__)
 #define USDT_NOP			nop 0
-#elif defined(__x86_64__)
-#define USDT_NOP                       .byte 0x90, 0x0f, 0x1f, 0x44, 0x00, 0x0 /* nop, nop5 */
 #else
 #define USDT_NOP			nop
 #endif