riscv: cmpxchg: Use riscv_has_extension_likely

Use riscv_has_extension_likely() to check for RISCV_ISA_EXT_ZAWRS,
replacing the use of asm goto with ALTERNATIVE.

The "likely" variant is used to match the behavior of the original
implementation using ALTERNATIVE("j %l[no_zawrs]", "nop", ...).

Signed-off-by: Vivian Wang <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Paul Walmsley <[e-mail]>

arch/riscv/include/asm/cmpxchg.h

···
 	u32 *__ptr32b;
 	ulong __s, __val, __mask;
 
-	asm goto(ALTERNATIVE("j %l[no_zawrs]", "nop",
-			     0, RISCV_ISA_EXT_ZAWRS, 1)
-		 : : : : no_zawrs);
+	if (!riscv_has_extension_likely(RISCV_ISA_EXT_ZAWRS)) {
+		ALT_RISCV_PAUSE();
+		return;
+	}
 
 	switch (size) {
 	case 1:
···
 	default:
 		BUILD_BUG();
 	}
-
-	return;
-
-no_zawrs:
-	ALT_RISCV_PAUSE();
 }
 
 #define __cmpwait_relaxed(ptr, val) \