usb: ums: fix disk capacity miscalculation and code cleanup
This patch prevents:
- ums disk capacity miscalculation because of integer overflow
Changes v2:
- Prevents passing zero size disk capacity to ums gadget driver
- Change function ums_get_capacity() to ums_disk_init() and do ums disk
initialization before gadget init
- Remove unnecessary code from mass storage driver
Signed-off-by: Przemyslaw Marczak <p.marczak@samsung.com> Cc: Marek Vasut <marex@denx.de>