qcom: usb: force apq8084 to diag,adb composition

Currently apq8084 is booting using the USB 2.0 controller. However,
on this target, this controller is limited in the number of endpoints
supported, hence we can only support at most two or three functions.
Set the default composition to diag,adb for now until the USB 3.0
controller is fully functional.

Change-Id: Id01c0bf929e01120ca406abd57f0e492316ce11e
common: Create usbdisk.img file with FAT32 file system

This change adds usbdisk.img file with FAT32 file system using
size provided from platform specific makefile.

Change-Id: Ica6a60bf7bf54e542de6b3cef57bd5d89a9fd353
Merge "qcom: usb: force apq8084 to diag,adb composition"
Merge "common: Create usbdisk.img file with FAT32 file system"