[ARM] 4226/1: initial .data and .bss mappings of XIP kernel should be TEXT_OFFSET

[ARM] 4226/1: initial .data and .bss mappings of XIP kernel should be TEXT_OFFSET
 aware

Since TEXT_OFFSET is meant to determine RAM location for kernel use,
itshould affect .data and .bss initial mapping in the XIP case.
Otherwise a XIP kernel would crash if TEXT_OFFSET gets somewhat larger
than 2MB.

Corresponding code is also moved up a bit to be near the similar .text
mapping code making the whole a bit more straight forward to understand.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>