ARM: OMAP2+: Fix null hwmod for ti-sysc debug

We may call omap_hwmod_parse_module_range() with no hwmod allocated yet
and may have debug enabled. Let's fix this by checking for hwmod before
trying to use it's name.

Fixes: 6c72b355 ("ARM: OMAP2+: Parse module IO range from dts for legacy
Signed-off-by: Tony Lindgren <tony@atomide.com>