flash: add device ID for Microchip PIC32 internal flash.

Microchip PIC32 has internal parallel flash (non-CFI compliant).
These flash devices do not support any identifier command so no
standard IDs. Added unique IDs to seperate these flash devices
from others supported by U-Boot.

Signed-off-by: Purna Chandra Mandal <purna.mandal@microchip.com>