ARM: dts: NSP: Fix amount of RAM on BCM958625HR

ARM: dts: NSP: Fix amount of RAM on BCM958625HR

Jon attempted to fix the amount of RAM on the BCM958625HR in commit
deefcc4c40d9 ("ARM: dts: NSP: Correct RAM amount for BCM958625HR board")
but it seems like we tripped over some poorly documented schematics.

The top-level page of the schematics says the board has 2GB, but when
you end-up scrolling to page 6, you see two chips of 4GBit (512MB) but
what the bootloader really initializes only 512MB, any attempt to use
more than that results in data aborts. Fix this again back to 512MB.

Fixes: deefcc4c40d9 ("ARM: dts: NSP: Correct RAM amount for BCM958625HR board")
Acked-by: Jon Mason <jon.mason@broadcom.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>