Multimedia: tidy DMABuf and texture helper sources


* include cleanup
* remove extra semicolon

Pick-to: 6.12
Change-Id: Ia7073fe0ebd51c1bbe3a24bfc6f9ccb7e004af7c
Reviewed-by: Artem Dyomin <artem.dyomin@qt.io>
commit61e6891e4c199ae2cec7bd22edc153007af59494
parente365857fcf92a28108a27bf48d0cecd53d7c855a
authorTim Blechmann <tim.blechmann@qt.io>
committerTim Blechmann <tim.blechmann@qt.io>
commit timeTue, 20 Oct 2026 12:37:59 +0000