ice: Fix bugs in control queue processing

This patch is a consolidation of multiple bug fixes for control queue
processing.

1)  In ice_clean_adminq_subtask() remove unnecessary reads/writes to
    registers. The bits PFINT_FW_CTL, PFINT_MBX_CTL and PFINT_SB_CTL
    are not set when an interrupt arrives, which means that clearing them
    again can be omitted.

2)  Get an accurate value in "pending" by re-reading the control queue
    head register from the hardware.

3)  Fix a corner case involving lost control queue messages by checking
    for new control messages (using ice_ctrlq_pending) before exiting the
    cleanup routine.

Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@intel.com>
Tested-by: Tony Brelinski <tonyx.brelinski@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>