pwm: Let PWM_CLPS711X depend on HAS_IOMEM

PWM_CLPS711X needs HAS_IOMEM, so depend on it, the related error (with
allmodconfig under um):

    MODPOST 1205 modules
  ERROR: "devm_ioremap_resource" [drivers/pwm/pwm-clps711x.ko] undefined!
  ERROR: "devm_ioremap" [drivers/net/phy/mdio-bcm-unimac.ko] undefined!
Signed-off-by: NChen Gang <gang.chen.5i5j@gmail.com>
Signed-off-by: NThierry Reding <thierry.reding@gmail.com>

drivers/pwm/Kconfig

@@ -83,6 +83,7 @@ config PWM_BFIN
 config PWM_CLPS711X
 	tristate "CLPS711X PWM support"
 	depends on ARCH_CLPS711X || COMPILE_TEST
+	depends on HAS_IOMEM
 	help
 	  Generic PWM framework driver for Cirrus Logic CLPS711X.