checkpatch: accept qca.qualcomm email addresses

@qca.qualcomm.com identities are allowed, hence
change the signed-off and author email validation to
accept @qca.qualcomm.com email addresses.

Change-Id: I8757226f53826c0e5e2825ebe89e80e10a2f18bb
Signed-off-by: Maya Erez <merez@codeaurora.org>