reset: uniphier: add reset controller driver for UniPhier SoCs

This is the initial commit for UniPhier reset controller driver.
Most code was ported from Linux.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 2d3303b..b64f6d8 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -817,6 +817,7 @@
 	select DM_GPIO
 	select DM_I2C
 	select DM_MMC
+	select DM_RESET
 	select DM_SERIAL
 	select DM_USB
 	select OF_CONTROL