USB: gadget: Compilation fixes for 64-bit support

After enabling USB drivers on arm-64 config, compiler
is raising issues related to mismatch in data size
and print format specifier on 32-bit and 64-bit. Fix
these errors.

Change-Id: I9590c92fb781b920b2536229fd9b637da9f4c594
Signed-off-by: Sujeet Kumar <ksujeet@codeaurora.org>