drivers/firmware/iscsi_ibft.c: make 3 functions static

This patch makes the following needlessly global functions static:
- ibft_attr_show_initiator()
- ibft_attr_show_nic()
- ibft_attr_show_target()

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Konrad Rzeszutek <ketuzsezr@darnok.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>