ASN.1: Fix check for strdup() success

It seems there is a misprint in the check of strdup() return code that
can lead to NULL pointer dereference.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 4520c6a ("X.509: Add simple ASN.1 grammar compiler")
Signed-off-by: Ekaterina Orlova <[email protected]>
Cc: David Woodhouse <[email protected]>
Cc: James Bottomley <[email protected]>
Cc: Jarkko Sakkinen <[email protected]>
Cc: [email protected]
Cc: [email protected]
Link: https://lore.kernel.org/r/[email protected]/
Signed-off-by: David Howells <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

scripts/asn1_compiler.c

@@ -625,7 +625,7 @@ int main(int argc, char **argv)
 	p = strrchr(argv[1], '/');
 	p = p ? p + 1 : argv[1];
 	grammar_name = strdup(p);
-	if (!p) {
+	if (!grammar_name) {
 		perror(NULL);
 		exit(1);
 	}