ARM: omap: remove debug-leds driver

It has been impossible to select this driver for six years
without anyone noticing, so just kill it completely.

Fixes: 54ea18e8

 ("ARM: OMAP2+: Remove board file for H4")
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>