spi: dw-bt1: Fix undefined devm_mux_control_get symbol

I mistakenly added the select attributes to the SPI_DW_BT1_DIRMAP config
instead of having them defined in SPI_DW_BT1. If the kernel doesn't have
the MULTIPLEXER and MUX_MMIO configs manually enabled and the
SPI_DW_BT1_DIRMAP config hasn't been selected, Baikal-T1 SPI device will
always fail to be probed by the driver. Fix that and the error reported by
the test robot:

>> ld.lld: error: undefined symbol: devm_mux_control_get
   >>> referenced by spi-dw-bt1.c
   >>> spi/spi-dw-bt1.o:(dw_spi_bt1_sys_init) in archive drivers/built-in.a

by moving the MULTIPLEXER/MUX_MMIO configs selection to the SPI_DW_BT1
config.

Link: https://lore.kernel.org/lkml/202011161745.uYRlekse-lkp@intel.com/
Link: https://lore.kernel.org/linux-spi/20201116040721.8001-1-rdunlap@infradead.org/
Fixes: abf00907

 ("spi: dw: Add Baikal-T1 SPI Controller glue driver")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Ramil Zaripov <Ramil.Zaripov@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20201127144612.4204-1-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>