Fix link error when TOUCHSCREEN_RASPBERRYPI_FW is enabled as a module and
the dependent module is built-in.  The 'depends on RASPBERRYPI_FIRMWARE' by
itself prevents the touchscreen driver from being built-in when the
firmware is configured as a module.  However, the '|| COMPILE_TEST' still
allows it unless we explicitly prevent that configuration with
'|| (RASPBERRYPI_FIRMWARE=n && COMPILE_TEST)'.

ld: drivers/input/touchscreen/raspberrypi-ts.o: in function `rpi_ts_probe':
raspberrypi-ts.c:(.text+0x3a8): undefined reference to `rpi_firmware_get'
ld: raspberrypi-ts.c:(.text+0x3a8): relocation truncated to fit: R_AARCH64_CALL26 against undefined symbol `rpi_firmware_get'
ld: raspberrypi-ts.c:(.text+0x4c8): undefined reference to `rpi_firmware_property'
ld: raspberrypi-ts.c:(.text+0x4c8): relocation truncated to fit: R_AARCH64_CALL26 against undefined symbol `rpi_firmware_property'

Rework so that TOUCHSCREEN_RASPBERRYPI_FW depends on
RASPBERRYPI_FIRMWARE=n if COMPILE_TEST is enabled.

Fixes: 0b9f28fe ("Input: add official Raspberry Pi's touchscreen driver")
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>