power: reset: Add MFD_SYSCON depends for brcmstb

The Broadcom STB reboot driver depends on MFD_SYSCON, it uses
syscon_regmap_lookup_by_phandle() which will not lookup syscon phandles
if MFD_SYSCON is disabled, and instead will return -ENOSYS since it is
turned into an inline stub.

Fixes: 030494e ("power: reset: Add reboot driver for brcmstb")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>

drivers/power/reset/Kconfig

@@ -41,6 +41,7 @@ config POWER_RESET_AXXIA
 config POWER_RESET_BRCMSTB
 	bool "Broadcom STB reset driver"
 	depends on ARM || MIPS || COMPILE_TEST
+	depends on MFD_SYSCON
 	default ARCH_BRCMSTB
 	help
 	  This driver provides restart support for Broadcom STB boards.