spi: rb4xx: Don't leak SPI master in probe error path

If the calls to devm_clk_get(), devm_spi_register_master() or
clk_prepare_enable() fail on probe of the Mikrotik RB4xx SPI driver,
the spi_master struct is erroneously not freed.

Fix by switching over to the new devm_spi_alloc_master() helper.

Fixes: 05aec357 ("spi: Add SPI driver for Mikrotik RB4xx series boards")
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: <stable@vger.kernel.org> # v4.2+: 5e844cc3: spi: Introduce device-managed SPI controller allocation
Cc: <stable@vger.kernel.org> # v4.2+
Cc: Bert Vermeulen <bert@biot.com>
Link: https://lore.kernel.org/r/369bf26d71927f60943b1d9d8f51810f00b0237d.1607286887.git.lukas@wunner.de


Signed-off-by: Mark Brown <broonie@kernel.org>