verify: add verify mode for a pattern with header

verify: add verify mode for a pattern with header

Add a verify=pattern_hdr option. Previously this was only available when
verify_pattern was set and verify= was omitted. Add a means to
explicitly select this verificaiton mode.

This is useful in the t/verify.py test script because it's troublesome
to have some jobs with a verify= option and omit this option in other
jobs when we want to test pattern verification with a header.

Link: https://lore.kernel.org/r/20250508185832.3702-2-vincent.fu@samsung.com
Signed-off-by: Vincent Fu <vincent.fu@samsung.com>