lib: Add a generic cmdline parse function parse_option_str

There should be a generic function to parse params like a=b,c
Adding parse_option_str in lib/cmdline.c which will return true
if there's specified option set in the params.

Also updated efi=old_map parsing code to use the new function

Signed-off-by: Dave Young <dyoung@redhat.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>

arch/x86/platform/efi/efi.c

@@ -932,26 +932,8 @@ u64 efi_mem_attributes(unsigned long phys_addr)
 
 static int __init parse_efi_cmdline(char *str)
 {
-	if (*str == '=')
-		str++;
-
-	while (*str) {
-		if (!strncmp(str, "old_map", 7)) {
-			set_bit(EFI_OLD_MEMMAP, &efi.flags);
-			str += strlen("old_map");
-		}
-
-		/*
-		 * Skip any options we don't understand. Presumably
-		 * they apply to the EFI boot stub.
-		 */
-		while (*str && *str != ',')
-			str++;
-
-		/* If we hit a delimiter, skip it */
-		if (*str == ',')
-			str++;
-	}
+	if (parse_option_str(str, "old_map"))
+		set_bit(EFI_OLD_MEMMAP, &efi.flags);
 
 	return 0;
 }