mmc: mmc_spi: Allow the driver to be built when CONFIG_HAS_DMA is unset

The commit cd57d07b1e4e ("sh: don't allow non-coherent DMA for NOMMU") made
CONFIG_NO_DMA to be set for some platforms, for good reasons.
Consequentially, CONFIG_HAS_DMA doesn't get set, which makes the DMA
mapping interface to be built as stub functions, but also prevent the
mmc_spi driver from being built as it depends on CONFIG_HAS_DMA.

It turns out that for some odd cases, the driver still relied on the DMA
mapping interface, even if the DMA was not actively being used.

To fixup the behaviour, let's drop the build dependency for CONFIG_HAS_DMA.
Moreover, as to allow the driver to succeed probing, let's move the DMA
initializations behind "#ifdef CONFIG_HAS_DMA".

Fixes: cd57d07b1e4e ("sh: don't allow non-coherent DMA for NOMMU")
Reported-by: Rich Felker <dalias@libc.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Rich Felker <dalias@libc.org>
Link: https://lore.kernel.org/r/20200901150438.228887-1-ulf.hansson@linaro.org
diff --git a/drivers/mmc/host/Kconfig b/drivers/mmc/host/Kconfig
index 9c89a5b..9a34c82 100644
--- a/drivers/mmc/host/Kconfig
+++ b/drivers/mmc/host/Kconfig
@@ -602,7 +602,7 @@
 
 config MMC_SPI
 	tristate "MMC/SD/SDIO over SPI"
-	depends on SPI_MASTER && HAS_DMA
+	depends on SPI_MASTER
 	select CRC7
 	select CRC_ITU_T
 	help