firmware_loader: Split sysfs support from fallback

In preparation for sharing the "loading" and "data" sysfs nodes with the
new firmware upload support, split out sysfs functionality from fallback.c
and fallback.h into sysfs.c and sysfs.h. This includes the firmware
class driver code that is associated with the sysfs files and the
fw_fallback_config support for the timeout sysfs node.

CONFIG_FW_LOADER_SYSFS is created and is selected by
CONFIG_FW_LOADER_USER_HELPER in order to include sysfs.o in
firmware_class-objs.

This is mostly just a code reorganization. There are a few symbols that
change in scope, and these can be identified by looking at the header
file changes. A few white-space warnings from checkpatch are also
addressed in this patch.

Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Tianfei zhang <tianfei.zhang@intel.com>
Tested-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
Signed-off-by: Russ Weight <russell.h.weight@intel.com>
Link: https://lore.kernel.org/r/20220421212204.36052-4-russell.h.weight@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>