sfxge(4): cleanup: add efsys_lock_state_t for type of state param in EFSYS_LOCK()

This allows the common code to use the correct type for the lock state
local variable passed to EFSYS_LOCK() and EFSYS_UNLOCK().

On Windows, this allows warning supression pragmas to be removed.

Submitted by: Andy Moreton <amoreton at solarflare.com>
Sponsored by: Solarflare Communications, Inc.
MFC after: 2 days