arm: omap2plus: Move CONFIG_SYS_PTV out of CONFIG namespace

This is always defined to 2, and referenced in two places.  Move the
define to <asm/omap_common.h> and make sure the code that uses this
includes that file.  Make <asm/arch-omap*/clock.h> not include that
file, as we don't need to be doing so.

Signed-off-by: Tom Rini <trini@konsulko.com>