asm: add missing .note.GNU-stack markers

Add .note.GNU-stack section declarations to hand-written assembly
sources so ELF builds do not produce executables or libraries with
an executable stack.

These assembly implementations do not require an executable stack.
Adding the marker restores normal non-executable stack/NX hardening.

Signed-off-by: hrimfaxi <outmatch@gmail.com>

src/gf128_arm64.S

@@ -99,4 +99,6 @@ func(gf128_mul):
 
 	ret
 
-
+#ifdef __ELF__
+.section .note.GNU-stack,"",@progbits
+#endif

src/sm2_z256_amd64.S

@@ -2139,3 +2139,6 @@ func(sm2_z256_point_add_affine):
 	popq	%rbp
 	.byte	0xf3,0xc3
 
+#if defined(__linux__) && defined(__ELF__)
+.section .note.GNU-stack,"",@progbits
+#endif

src/sm2_z256_arm64.S

@@ -2210,3 +2210,6 @@ func(sm2_z256_modn_mont_sqr):
 	ldp	x29,x30,[sp],#64
 	ret
 
+#ifdef __ELF__
+.section .note.GNU-stack,"",@progbits
+#endif

src/sm9_z256_arm64.S

@@ -895,3 +895,6 @@ func(sm9_z256_modp_mont_sqr):
 	ldp	x29,x30,[sp],#64
 	ret
 
+#ifdef __ELF__
+.section .note.GNU-stack,"",@progbits
+#endif