OMAP2420: CTRL: fix OMAP242X_CTRL_REGADDR macro

Conform the OMAP2420_CTRL_BASE macro name to the standard of the rest of the
OMAP*_CTRL_BASE macro names.  This fixes a bug in the OMAP2420 SCM code that
prevented OMAP242X_CTRL_REGADDR from working.

Signed-off-by: Paul Walmsley <paul@pwsan.com>