usb: host: xhci-tegra: Separate firmware request and load

usb: host: xhci-tegra: Separate firmware request and load

Subsequent patches for system suspend/resume support will need to reload
the firmware on resume. Since the firmware remains in system memory, the
driver doesn't need to reload it from the filesystem. However, the XUSB
controller will be reset across suspend/resume, so it needs to load the
firmware into its microcontroller on resume.

Split the firmware request and the firmware load code into two separate
functions so that the driver can reuse the firmware in system memory to
reload the microcontroller on resume.

Based on work by JC Kuo <jckuo@nvidia.com>.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20191206140653.2085561-3-thierry.reding@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>