ARM: dts: rockchip: rk3368-sheep add vsel gpio for syr827

ARM: dts: rockchip: rk3368-sheep add vsel gpio for syr827

Add vsel gpio for syr827, which is PMIC_SLEEP in hardware pcb.

The driver will parse the gpio and use it to indicate the chip
work status, as the following codes:

static int fan53555_is_enabled ()
	if defined vsel_gpio
		gpiod_get_raw_value
	else
		regmap_read

Before the patch, the log shows:
	CPU4: update cpu_capacity 1024
	CPU4: Booted secondary processor [410fd033]
	  cache: parent cpu4 should not be sleeping
	rk3x-i2c ff650000.i2c: timeout, ipd: 0x10, state: 1

Since cpu4 is the base core for cluster1, which need to initialize
cpufreq during boot up, finally call fan53555_is_enabled. But the
i2c is suspended at that time, can't get interrupt until timeout.

Change-Id: I301e95be3b60d2faa456759d88c06cf64c2019ca
Signed-off-by: Jianqun Xu <jay.xu@rock-chips.com>