mtd: lantiq-flash: drop check of boot select

Do not check which flash type the SoC was booted from before
using this driver. Assume that the device tree is correct and use this
driver when it was added to device tree. This also removes a build
dependency to the SoC code.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Acked-by: Brian Norris <computersforpeace@gmail.com>
Cc: martin.blumenstingl@googlemail.com
Cc: john@phrozen.org
Cc: robh@kernel.org
Cc: andy.shevchenko@gmail.com
Cc: p.zabel@pengutronix.de
Cc: kishon@ti.com
Cc: mark.rutland@arm.com
Cc: linux-mips@linux-mips.org
Cc: linux-mtd@lists.infradead.org
Cc: linux-watchdog@vger.kernel.org
Cc: devicetree@vger.kernel.org
Cc: linux-spi@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/17117/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>