memory: brcmstb_memc: Simplify compatible matching

memory: brcmstb_memc: Simplify compatible matching

Now that a "brcm,brcmstb-memc-ddr-rev-b.2.x" fallback compatible string
has been defined, we can greatly simplify the matching within the driver
to only look for that compatible string and nothing else.

The fallback "brcm,brcmstb-memc-ddr" is also updated to assume the V21
register layout since that is the most common nowadays.

Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://lore.kernel.org/r/20250609212356.2264244-3-florian.fainelli@broadcom.com
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>