ARM: dts: NSP: Correct FA2 mailbox node

The FA2 mailbox is specified at 0x18025000 but should actually be
0x18025c00, length 0x400 according to socregs_nsp.h and board_bu.c. Also
the interrupt was off by one and should be GIC SPI 151 instead of 150.

Fixes: 17d51717

 ("ARM: dts: NSP: Add mailbox (PDC) to NSP")
Signed-off-by: Matthew Hagan <mnhagan88@gmail.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>