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

This achieves two goals:

1) Get rid of davinci_uart_v2p() and davinci_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.

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