staging: gdm72xx: Simplify spinlock fix for gdm_usb_send_complete

This patch simplifies the previous patch (commit
dd13c86b

) for fixing the spinlock
recursion issue on several call sites of gdm_usb_send_complete.

Signed-off-by: Ben Chan <benchan@chromium.org>
Cc: Sage Ahn <syahn@gctsemi.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>