Add cfi directives to x86 syscalls.

Modify the syscalls script to generate the cfi directives for x86
syscalls.

Update the x86 syscalls.

Change-Id: Ia1993dc714a7e79f917087fff8200e9a02c52603

libc/arch-x86/syscalls/signalfd4.S

@@ -7,6 +7,11 @@ ENTRY(signalfd4)
     pushl   %ecx
     pushl   %edx
     pushl   %esi
+    .cfi_def_cfa_offset 16
+    .cfi_rel_offset ebx, 0
+    .cfi_rel_offset ecx, 4
+    .cfi_rel_offset edx, 8
+    .cfi_rel_offset esi, 12
     mov     20(%esp), %ebx
     mov     24(%esp), %ecx
     mov     28(%esp), %edx