arm: dra76: fastboot: extend cpu type for getvar command

'commit dda0bd674481 ("arm: dra762: Add support for device package identification")'
introduces ABZ and ACD package identification.

This patch is to extend usage of "fastboot getvar cpu" for
DRA76x ABZ and ACD devices.

Helps in fixing the boot warning.

Warning: fastboot.cpu: unknown CPU rev: 123863298
on
CPU  : DRA762-GP ES1.0 ABZ package
Model: TI AM5748 IDK
Board: AM574x IDK REV 1.0A

Signed-off-by: Praneeth Bajjuri <praneeth@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>