Revert "firmware: add sanity check on shutdown/suspend"

This reverts commit 81f9507628.

It causes random failures of firmware loading at resume time (well,
random for me, it seems to be more reliable for others) because the
firmware disabling is not actually synchronous with any particular
resume event, and at least the btusb driver that uses a workqueue to
load the firmware at resume seems to occasionally hit the "firmware
loading is disabled" logic because the firmware loader hasn't gotten the
resume event yet.

Some kind of sanity check for not trying to load firmware when it's not
possible might be a good thing, but this commit was not it.

Greg seems to have silently suffered the same issue, and pointed to the
likely culprit, and Gabriel C verified the revert fixed it for him too.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Pointed-at-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Tested-by: Gabriel C <nix.or.die@gmail.com>
Cc: Luis R. Rodriguez <mcgrof@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/driver-api/firmware/request_firmware.rst

@@ -44,17 +44,6 @@ request_firmware_nowait
 .. kernel-doc:: drivers/base/firmware_class.c
    :functions: request_firmware_nowait
 
-Considerations for suspend and resume
-=====================================
-
-During suspend and resume only the built-in firmware and the firmware cache
-elements of the firmware API can be used. This is managed by fw_pm_notify().
-
-fw_pm_notify
-------------
-.. kernel-doc:: drivers/base/firmware_class.c
-   :functions: fw_pm_notify
-
 request firmware API expected driver use
 ========================================