soc: bcm: brcmstb: pm: Add support for newer rev B3.0 controllers

Update the Device Tree binding document and add a matching entry for the
MEMC DDR controller revision B3.0 which is found on chips like 7278A0
and newer.

Signed-off-by: Doug Berger <[e-mail]>
[florian: tweak commit message, make it apply to upstream kernel]
Reviewed-by: Rob Herring <[e-mail]>
Signed-off-by: Florian Fainelli <[e-mail]>

Documentation/devicetree/bindings/arm/bcm/brcm,brcmstb.txt

···
 Required properties:
 - compatible     : should contain one of these
 	"brcm,brcmstb-memc-ddr-rev-b.2.2"
+	"brcm,brcmstb-memc-ddr-rev-b.3.0"
 	"brcm,brcmstb-memc-ddr"
 - reg            : the MEMC DDR register range
 

drivers/soc/bcm/brcmstb/pm/pm-arm.c

···
 		.data = &ddr_seq_b22,
 	},
 	{
+		.compatible = "brcm,brcmstb-memc-ddr-rev-b.3.0",
+		.data = &ddr_seq_b22,
+	},
+	{
 		.compatible = "brcm,brcmstb-memc-ddr",
 		.data = &ddr_seq,
 	},