scripts: sercomm-pid.py: use uppercase hwid in pid

scripts: sercomm-pid.py: use uppercase hwid in pid

Sercomm uses uppercase for hexadecimal representation of the device
hardware IDs in factory image PID. This commit brings the sercomm-pid.py
script into compliance with the original Sercomm algorithm.

Example
-------
+--------+-------------+-----------+-------------+
| Device | PID (before | PID       | PID (after  |
| HWID   | the commit) | (Sercomm) | the commit) |
+--------+-------------+-----------+-------------+
| CPJ    | 43 50 4a    | 43 50 4A  | 43 50 4A    |
+--------+-------------+-----------+-------------+

Signed-off-by: Mikhail Zhilkin <csharper2005@gmail.com>