armv7a: read ttbcr and ttb0/1 at every entry in debug state

armv7a: read ttbcr and ttb0/1 at every entry in debug state

Commit bfc5c764df145f68835543119865eabe462e19c2 avoids reading
ttbcr and ttb0/1 at every virt2phys translation by caching them,
and it updates the cached values in armv7a_arch_state().
But the purpose of any (*arch_state)() method, thus including
armv7a_arch_state(), is to only print out and inform the user
about some architecture specific status.
Moreover, to reduce the verbosity during a GDB session, the
method (*arch_state)() is not executed anymore at debug state
entry (check use of target->verbose_halt_msg in src/openocd.c),
thus the state of translation table gets out-of-sync triggering
	Error: Address translation failure
or even using a wrong address in the memory R/W operation.

In addition, the commit above breaks the case of armv7r by
calling armv7a_read_ttbcr() unconditionally.

Fixed by moving in cortex_a_post_debug_entry() the call to
armv7a_read_ttbcr() on armv7a case only.
Remove the call to armv7a_read_ttbcr() in armv7a_identify_cache()
since it is (conditionally) called only in the same procedure
cortex_a_post_debug_entry().

Fixes: bfc5c764df14 ("armv7a: cache ttbcr and ttb0/1 on debug
state entry")
Change-Id: Ifc20eca190111832e339a01b7f85d28c1547c8ba
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/4601
Tested-by: jenkins
Reviewed-by: Matthias Welwarsky <matthias@welwarsky.de>