Staging: btmtk_usb: Fix Sparse Warning of incorrect casting

This patch fixes the following Sparse Warnings in btmtk_usb.c:

drivers/staging/btmtk_usb/btmtk_usb.c:110:16: warning: cast to restricted __le32
drivers/staging/btmtk_usb/btmtk_usb.c:299:23: warning: cast to restricted __le16

Signed-off-by: Rashika Kheria <rashika.kheria@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>