reset: Add generic reset driver

This patch adds a generic reset driver. It is designed to be useful when
one has a register in a regmap which contains bits that reset other
devices. I thought this seemed like a very generic use, so here is a
generic driver. The overall structure has been modeled on the syscon-reboot
driver.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/sandbox_defconfig b/configs/sandbox_defconfig
index 692432c..ee1e6f3 100644
--- a/configs/sandbox_defconfig
+++ b/configs/sandbox_defconfig
@@ -196,6 +196,8 @@
 CONFIG_DM_RESET=y
 CONFIG_SANDBOX_RESET=y
 CONFIG_DM_RNG=y
+CONFIG_RNG_SANDBOX=y
+CONFIG_RESET_SYSCON=y
 CONFIG_DM_RTC=y
 CONFIG_RTC_RV8803=y
 CONFIG_SANDBOX_SERIAL=y