testsuite: Partially fix up modref-*.c tests

testsuite: Partially fix up modref-*.c tests

This ia a partial attempt to fix:
FAIL: gcc.dg/ipa/modref-1.c (test for excess errors)
FAIL: gcc.dg/ipa/modref-1.c scan-ipa-dump modref "param offset: 1"
FAIL: gcc.dg/ipa/modref-1.c scan-ipa-dump modref "param offset: 2"
FAIL: gcc.dg/tree-ssa/modref-4.c (test for excess errors)
FAIL: gcc.dg/tree-ssa/modref-4.c scan-tree-dump modref1 "param offset: 1"
UNRESOLVED: gcc.dg/tree-ssa/modref-4.c scan-tree-dump modref2 "param offset: 2"
UNRESOLVED: gcc.dg/tree-ssa/modref-4.c scan-tree-dump modref2 "return 0"
The return 0 scan still FAILs.

2020-10-15  Jakub Jelinek  <jakub@redhat.com>

	* gcc.dg/ipa/modref-1.c: Remove space between param offset: and number
	in scan-ipa-dump.
	(b): Declare return type to void.
	(main): Declare return type to int.  Change c to array of 3 chars.
	* gcc.dg/tree-ssa/modref-4.c: Remove space between param offset: and
	number in scan-ipa-dump.  Use modref1 instead of modref2.
	(b): Declare return type to void.
	(main): Declare return type to int.  Change c to array of 3 chars.