pwm: aspeed: Select SYSCON to get parent detail.

To work correctly, this driver depends on SYSCON to get the base address
from the parent dts node.

Signed-off-by: Billy Tsai <billy_tsai@aspeedtech.com>
Reviewed-by: Chia-Wei Wang <chiawei_wang@aspeedtech.com>

drivers/pwm/Kconfig

@@ -12,6 +12,7 @@ config DM_PWM
 config PWM_ASPEED
 	bool "Enable support for the Aspeed PWM"
 	depends on DM_PWM
+	select SYSCON
 	help
 	  This PWM is found on Ast2600 SoCs. It supports a programmable period
 	  and duty cycle. It provides 16 channels which can be independently