rs6000: Don't forget to initialize the TOC (PR77957)

rs6000: Don't forget to initialize the TOC (PR77957)

The code generating traceback tables mistakenly does an early return
if !optional_tbtab, which causes it to miss the code generating the TOC
section.  This only matters if the TOC will be empty since otherwise
the section is created elsewhere.

This patch fixes it.

	PR target/77957
	* config/rs6000/rs6000.c (rs6000_output_function_epilogue): Don't
	return early if !optional_tbtab.

From-SVN: r242336