texi2pod.pl: add no-op --no-split option support [PR28144]

Change 2faf902d ("generate single html manual page by default")
added use of --no-split option to makeinfo. binutils reuses
makeinfo options for texi2pod.pl wrapper. Unsupported option
led to silent manpage truncation.

The change adds no-op option support.

etc/
	PR 28144
	* texi2pod.pl: Handle no-op --no-split option.

(cherry picked from commit 96a7037c)