soc: bcm2835: Make !RASPBERRYPI_FIRMWARE dummies return failure

soc: bcm2835: Make !RASPBERRYPI_FIRMWARE dummies return failure

[ Upstream commit 144345a4a8c3b497a3f60d3af9d6071a37660186 ]

If CONFIG_RASPBERRYPI_FIRMWARE=n:

    drivers/gpio/gpio-raspberrypi-exp.c: In function ‘rpi_exp_gpio_get_polarity’:
    drivers/gpio/gpio-raspberrypi-exp.c:71: warning: ‘get.polarity’ is used uninitialized in this function
    drivers/gpio/gpio-raspberrypi-exp.c: In function ‘rpi_exp_gpio_get_direction’:
    drivers/gpio/gpio-raspberrypi-exp.c:150: warning: ‘get.direction’ is used uninitialized in this function

The dummy firmware interface functions return 0, which means success,
causing subsequent code to make use of the never initialized output
parameter.

Fix this by making the dummy functions return an error code (-ENOSYS)
instead.

Note that this assumes the firmware always fills in the requested data
in the CONFIG_RASPBERRYPI_FIRMWARE=y case.

Fixes: d45f1a563b92dac7 ("staging: vc04_services: fix up rpi firmware functions")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>