pwm: renesas-tpu: Add dependency on HAS_IOMEM

On archs like S390 or um this driver cannot build nor work.
Make it depend on HAS_IOMEM to bypass build failures.

drivers/built-in.o: In function `tpu_probe':
drivers/pwm/pwm-renesas-tpu.c:421: undefined reference to `devm_ioremap_resource'
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

drivers/pwm/Kconfig

@@ -160,6 +160,7 @@ config PWM_PXA
 config PWM_RENESAS_TPU
 	tristate "Renesas TPU PWM support"
 	depends on ARCH_SHMOBILE || COMPILE_TEST
+	depends on HAS_IOMEM
 	help
 	  This driver exposes the Timer Pulse Unit (TPU) PWM controller found
 	  in Renesas chips through the PWM API.