doc: fix typo in multiple directories before v4.2.0 release

Utilize a code spell-checking tool to scan for and correct spelling errors
in various files within the `doc` directory.

In `dsa_txrx_process.svg`, correct the typo `Tansmit` to `Transmit`.

Signed-off-by: Pisit Sawangvonganan <pisit@ndrsolution.com>