kernel: fix sdhci-msm build error

A missing upstream stable backport leads to the following build error:

     CC      drivers/mmc/host/sdhci-msm.o
    drivers/mmc/host/sdhci-msm.c:1158:3: error: 'const struct sdhci_ops' has no member named 'write_w'
      .write_w = sdhci_msm_write_w,
       ^~~~~~~
    drivers/mmc/host/sdhci-msm.c:1158:13: warning: excess elements in struct initializer
      .write_w = sdhci_msm_write_w,
                 ^~~~~~~~~~~~~~~~~
    drivers/mmc/host/sdhci-msm.c:1158:13: note: (near initialization for 'sdhci_msm_ops')
    scripts/Makefile.build:326: recipe for target 'drivers/mmc/host/sdhci-msm.o' failed

Solve the issue by backporting commit
99d570da30 ("mmc: Kconfig: Enable CONFIG_MMC_SDHCI_IO_ACCESSORS")
from linux-stable.

Ref: https://github.com/openwrt/openwrt/commit/528508ae8b33c76deaf18f313973144a7e920678#commitcomment-32049231
Fixes: 528508ae8b ("kernel: bump 4.14 to 4.14.95")
Signed-off-by: Jo-Philipp Wich <[email protected]>

target/linux/generic/backport-4.14/420-enable-CONFIG_MMC_SDHCI_IO_ACCESSORS.patch

@@ -0,0 +1,23 @@
+From: Vijay Viswanath <[email protected]>
+Date: Wed, 27 Sep 2017 11:04:42 +0530
+Subject: [PATCH v2 3/4] mmc: Kconfig: Enable CONFIG_MMC_SDHCI_IO_ACCESSORS
+
+Enable CONFIG_MMC_SDHCI_IO_ACCESSORS so that SDHC controller specific
+register read and write APIs, if registered, can be used.
+
+Signed-off-by: Vijay Viswanath <[email protected]>
+Acked-by: Adrian Hunter <[email protected]>
+---
+ drivers/mmc/host/Kconfig | 1 +
+ 1 file changed, 1 insertion(+)
+
+--- a/drivers/mmc/host/Kconfig
++++ b/drivers/mmc/host/Kconfig
+@@ -420,6 +420,7 @@ config MMC_SDHCI_MSM
+ 	tristate "Qualcomm SDHCI Controller Support"
+ 	depends on ARCH_QCOM || (ARM && COMPILE_TEST)
+ 	depends on MMC_SDHCI_PLTFM
++	select MMC_SDHCI_IO_ACCESSORS
+ 	help
+ 	  This selects the Secure Digital Host Controller Interface (SDHCI)
+ 	  support present in Qualcomm SOCs. The controller supports