MdeModulePkg/UsbMass: Fix integer overflow when BlockSize is 1

MdeModulePkg/UsbMass: Fix integer overflow when BlockSize is 1

UsbBootReadWriteBlocks() and UsbBootReadWriteBlocks16() use a UINT16
local variable to hold the value of
USB_BOOT_MAX_CARRY_SIZE (=0x10000) / BlockSize.
When BlockSize is 1, the UINT16 local variable is set to 0x10000
but the high-16 bits are truncated resulting the final value be 0.

It causes the while-loop in the two functions accesses 0 block in
each loop, resulting the loop never ends.

The patch fixes the two functions to make sure no integer overflow
happens.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Cc: Steven Shi <steven.shi@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>