Staging: emxx_udc: Fix do not add new typedefs and remove volatile

This patch fixes the following checkpatch.pl warnings:"do not add new
typedefs" and "Use of volatile is usually wrong".
Remove typedefs keyword and rename identifiers appropriately.
Remove volatile from union usb_regs_access
Update related  files.

Signed-off-by: Haneen Mohammed <hamohammed.sa@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>