commit 079fe5a6 upstream.

This function is shared between gadget functions, so this avoid unnecessary
duplicated code and potentially avoid memory leaks.
Reviewed-by: Robert Baldyga <r.baldyga@samsung.com>
Signed-off-by: Felipe F. Tonello <eu@felipetonello.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
[bwh: Backported to 3.16: adjust filenames]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>