fix incorrect escaping in add-cfi.*.awk scripts

gawk 5 complains.

tools/add-cfi.i386.awk

@@ -81,7 +81,7 @@ function adjust_sp_offset(delta) {
     in_function = 0
   }
 }
-/^\.type [a-zA-Z0-9_]+,\@function/ {
+/^\.type [a-zA-Z0-9_]+,@function/ {
   functions[substr($2, 1, length($2)-10)] = 1
 }
 # not interested in assembler directives beyond this, just pass them through

tools/add-cfi.x86_64.awk

@@ -76,7 +76,7 @@ function adjust_sp_offset(delta) {
     in_function = 0
   }
 }
-/^\.type [a-zA-Z0-9_]+,\@function/ {
+/^\.type [a-zA-Z0-9_]+,@function/ {
   functions[substr($2, 1, length($2)-10)] = 1
 }
 # not interested in assembler directives beyond this, just pass them through