Runtime constants: introduce omap2_set_globals_*()

Runtime constants: introduce omap2_set_globals_*()

Add the omap2_set_globals_{242x,243x,343x}() functions.  These
functions are called early upon boot in the map_io() functions in the
board-specific init files.  The functions are currently no-ops.  Later
patches augment these functions to set global variables to the base
virtual addresses of OMAP modules.  This makes it possible to write
code that can run without modification on multiple OMAP chip
revisions.

The *_set_globals_* functions are added into
arch/arm/plat-omap/common.c.  This patch currently only introduces
OMAP2 and OMAP3 functions, but a later patch introduces an
OMAP16XX-specific version, omap1_set_globals_16xx().

Also, while we are here, we get rid of the unused OMAP_L4_BASE define.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>