usb: gadget: change the minor number for android functions

Due to latest addition of android1 as a valid device
at commit 5a11767b (usb_bam: changes for HSIC IPA
functionality) there was a collision of the same minor
number for android1 and f_ffs. This caused removal of
the wrong device when the initial probe/init fails.
This commit fixes the initial index to 2 to prevent
a collision with android0 and android1.

Change-Id: Ie4379043bbd0bd200c6093e229ca54ecce66732f
Signed-off-by: Lena Salman <esalman@codeaurora.org>