wifi: mt76: Strip whitespace from build ddate

wifi: mt76: Strip whitespace from build ddate

On systems I have with mt7925 cards I've been noticing a blank line in my
kernel logs.  IE:
```
[   17.294105] mt7925e 0000:c3:00.0: HW/SW Version: 0x8a108a10, Build Time: 20250721232852a

[   17.314233] r8169 0000:c4:00.0 enp196s0f0: Link is Down
```

This is because the build_date from the header has a newline character
as does the dev_info() print.  As the firmware isn't guaranteed to always
have a newline but the print is, copy the firmware build date to a
temporary variable and strip any whitespace from it before showing it in
the logs.

Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
Link: https://patch.msgid.link/20251120155829.3494747-1-superm1@kernel.org
Signed-off-by: Felix Fietkau <nbd@nbd.name>