staging/gdm72xx: Include corresponding header file (fix sparse warning)

sdio_boot.c and netlink_k.c both have a corresponding header file with
their function prototypes but fail to include them, which leads to the
following sparse warnings:
sdio_boot.c:135:5: warning: symbol 'sdio_boot' was not declared. Should it be static?
netlink_k.c:89:13: warning: symbol 'netlink_init' was not declared. Should it be static?
netlink_k.c:109:6: warning: symbol 'netlink_exit' was not declared. Should it be static?
netlink_k.c:114:5: warning: symbol 'netlink_send' was not declared. Should it be static?

-> Add the include files and silence the warning

Signed-off-by: Peter Huewe <peterhuewe@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>