soc: bcm: brcmstb: Add missing DDR MEMC compatible strings

soc: bcm: brcmstb: Add missing DDR MEMC compatible strings

We would not be matching the following chip/compatible strings
combinations, which would lead to not setting the warm boot flag
correctly, fix that:

    7260A0/B0: brcm,brcmstb-memc-ddr-rev-b.2.1
    7255A0: brcm,brcmstb-memc-ddr-rev-b.2.3
    7278Bx: brcm,brcmstb-memc-ddr-rev-b.3.1

The B2.1 core (which is in 7260 A0 and B0) doesn't have the
SHIMPHY_ADDR_CNTL_0_DDR_PAD_CNTRL setup in the memsys init code, nor
does it have the warm boot flag re-definition on entry. Those changes
were for B2.2 and later MEMSYS cores. Fall back to the previous S2/S3
entry method for these specific chips.

Fixes: 0b741b8234c8 ("soc: bcm: brcmstb: Add support for S2/S3/S5 suspend states (ARM)")
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>