USB: io_ti: Fix firmware version handling

USB: io_ti: Fix firmware version handling

The io_ti driver fails to download firmware to Edgeport
devices such as the EP/416, even when the on-disk firmware image
(/lib/firmware/edgeport/down3.bin) is more current than the version
on the EP/416.  The current download code is broken in a few ways.
Notably it mis-uses global variables OperationalMajorVersion and
OperationalMinorVersion (reading their values before they've been
properly initialized and subsequently initializing them multiple times
without synchronization).  This patch drops the global variables and
replaces the redundant calls to request_firmware()/release_firmware()
in download_fw() with a single call pair in edge_startup(); the firmware
image pointer is then passed to download_fw() and build_i2c_fw_hdr().

Signed-off-by: Peter E. Berger <pberger@brimson.com>
Signed-off-by: Johan Hovold <johan@kernel.org>