usb_storage:Fix USB storage capacity detection on 64 bit architectures

This patch fixes USB storage capacity detection breakage on 64-bit systems
which arises due to 'unsigned long' length difference. Old code assumes that
to be 32 bit and breaks because of inappropriate response buffer layout.
Also this fixes a number of build warnings and changes big-endian values
treatment style to be architecture-independent

Signed-off-by: Sergey Temerkhanov <s.temerkhanov@gmail.com>
Signed-off-by: Radha Mohan Chintakuntla <rchintakuntla@cavium.com>