Increase max loop device number upto 255

Increase max loop device number upto 255

According to loop manual,
kernel provides the /dev/loop-control device since Linux 3.1,
which permits an application to dynamically find a free device,
and to add and remove loop devices from the system.

The limit is the maximum number of minor devices for a single major
device(since loop has a single major, block 7), which is limited by
MINORBITS which is located in kdev_t.h file of Linux.
Therefore, it actually 2 to the power of 20, just over a million.

In result, Linux could support lots number of loop devices.

To use more than 100 loop devices,
increase max loop device number in mic.

Change-Id: I2e763f3c70c5aa919e67621bc54d37c0def9d07b