Kconfig: retire empty <asm/barebox.h> ...

With the latest changes, this file is empty on all archs. Drop it.

Signed-off-by: Ahmad Fatoum <ahmad@a3f.at>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Kconfig: create Kconfig symbol for ARCH_HAS_DATA_ABORT_MASK ...

Other arch-specific features are exposed in Kconfig too, so do here
likewise.

Signed-off-by: Ahmad Fatoum <ahmad@a3f.at>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Limit data_abort_mask to !PBL ...

To make memory_display usable in PBL

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

ARM: Allow to mask data aborts ...

Sometimes it's useful to test if a memory operation works or
aborts. This adds data_abort_mask() to ignore data aborts and
data_abort_unmask() to enable them again. This is used in the
next step for the 'md' command so that illegal addresses just
show 'xxxxxxxx' instead of crashing the system.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>