dt-bindings: sy8824x: Document SY8824E support

SY8824E is an I2C-controlled adjustable voltage regulator made by
Silergy Corp. The only difference between SY8824C and SY8824E is the
vsel_min.
Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Link: https://lore.kernel.org/r/20190827163505.361890af@xhacker.debianSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/regulator/sy8824x.txt

-SY8824C Voltage regulator
+SY8824C/SY8824E Voltage regulator
 
 Required properties:
-- compatible: Must be "silergy,sy8824c"
+- compatible: Must be one of the following.
+	"silergy,sy8824c"
+	"silergy,sy8824e"
 - reg: I2C slave address
 
 Any property defined as part of the core regulator binding, defined in