utf8_to_ucs2() should check for malloc failure

utf8_to_ucs2() is calling malloc() without checking the result.

Reviewed by:	imp
Differential Revision:	https://reviews.freebsd.org/D13933

stand/efi/libefi/efichar.c

@@ -139,6 +139,8 @@ utf8_to_ucs2(const char *name, efi_char **nmp, size_t *len)
 	sz = strlen(name) * 2 + 2;
 	if (*nmp == NULL)
 		*nmp = malloc(sz);
+	if (*nmp == NULL)
+		return (ENOMEM);
 	nm = *nmp;
 	*len = sz;