ARM: mach-omap2: clean up debug-macro.S

This achieves two goals:

1) Get rid of omap_uart_v2p() and omap_uart_p2v() which were the last users
   of PLAT_PHYS_OFFSET.

2) Remove the probing of the M bit in the CP15 control reg and make
   the access to the .data variables completely position independent.

There is a catch though: the busyuart macro needs to know where the LSR
register is which might be at a different offset depending on the hardware.
Given that this macro is given only two registers and that one of them
must be preserved, the trick is to always pass the LSR register address
around, and deduce the base address for the THR register by masking out
the LSR offset in senduart instead.

Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Tested-by: Tony Lindgren <tony@atomide.com>
Reviewed-by: Kevin Hilman <khilman@ti.com>