i2c: mux: fix up dependencies

commit 93d710a65ef02fb7fd48ae207e78f460bd7a6089 upstream.

We get the following build error from UM Linux after adding
an entry to drivers/iio/gyro/Kconfig that issues "select I2C_MUX":

ERROR: "devm_ioremap_resource"
   [drivers/i2c/muxes/i2c-mux-reg.ko] undefined!
ERROR: "of_address_to_resource"
   [drivers/i2c/muxes/i2c-mux-reg.ko] undefined!

It appears that the I2C mux core code depends on HAS_IOMEM
for historical reasons, while CONFIG_I2C_MUX_REG does *not*
have a direct dependency on HAS_IOMEM.

This creates a situation where a allyesconfig or allmodconfig
for UM Linux will select I2C_MUX, and will implicitly enable
I2C_MUX_REG as well, and the compilation will fail for the
register driver.

Fix this up by making I2C_MUX_REG depend on HAS_IOMEM and
removing the dependency from I2C_MUX.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Reported-by: Jonathan Cameron <jic23@jic23.retrosnub.co.uk>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Jonathan Cameron <jic23@kernel.org>
Acked-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
index 78fbee4..65dbde7 100644
--- a/drivers/i2c/Kconfig
+++ b/drivers/i2c/Kconfig
@@ -59,7 +59,6 @@
 
 config I2C_MUX
 	tristate "I2C bus multiplexing support"
-	depends on HAS_IOMEM
 	help
 	  Say Y here if you want the I2C core to support the ability to
 	  handle multiplexed I2C bus topologies, by presenting each
diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
index f06b0e2..af2a63c 100644
--- a/drivers/i2c/muxes/Kconfig
+++ b/drivers/i2c/muxes/Kconfig
@@ -63,6 +63,7 @@
 
 config I2C_MUX_REG
 	tristate "Register-based I2C multiplexer"
+	depends on HAS_IOMEM
 	help
 	  If you say yes to this option, support will be included for a
 	  register based I2C multiplexer. This driver provides access to