mips: dts: Fix PIC32MZDA GPIO register definitions

The GPIO bank name for banks J and K are not correct when using the
'gpio' command from the console.

The driver derives the bank name from the device tree instance string by
using the instance value and adding 'A': gpio0@xxaddrxx is Bank A,
gpio1@yyaddryy is Bank B and so on.

On the PIC32, there is no Bank I so instances 8 and 9 need to be
incremented as a minimum change.

An alternative (less opaque) implementation would be to use a bank-name
property instead but this would require modifying the driver code too.

Signed-off-by: John Robertson <john.robertson@simiatec.com>