USB: f_mtp: Increase the IN endpoint buffer allocation

Some UDC may require allocation of some extra bytes for
TX buffer due to hardware requirement. Add necessary
changes for the same.

Change-Id: I7ebe4cfb1c1d6f4e6ab2914db5e7256003b4b638
Signed-off-by: Sujeet Kumar <ksujeet@codeaurora.org>
Signed-off-by: ChandanaKishori Chiluveru <cchilu@codeaurora.org>