gve: Return error for unknown admin queue command

gve: Return error for unknown admin queue command

[ Upstream commit b11344f63fdd9e8c5121148a6965b41079071dd2 ]

In gve_adminq_issue_cmd(), return -EINVAL instead of 0 when an unknown
admin queue command opcode is encountered.

This prevents the function from silently succeeding on invalid input
and prevents undefined behavior by ensuring the function fails gracefully
when an unrecognized opcode is provided.

These changes improve error handling.

Signed-off-by: Alok Tiwari <alok.a.tiwari@oracle.com>
Link: https://patch.msgid.link/20250616054504.1644770-2-alok.a.tiwari@oracle.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>