reset: Add STi reset support

This patch adds a reset controller implementation for STMicroelectronics
STi family SoCs; it allows a group of related reset like controls found
in multiple system configuration registers to be represented by a single
controller device.

Driver code has been mainly extracted from kernel
drivers/reset/sti/reset-stih407.c

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index dacfe9a..e644ee3 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1132,6 +1132,7 @@
 	select DM_SERIAL
 	select BLK
 	select DM_MMC
+	select DM_RESET
 	help
 	  Support for STMicroelectronics STiH407/10 SoC family.
 	  This SoC is used on Linaro 96Board STiH410-B2260