target: Add default implementation of bulk_write_memory

Remove dummy implementations from all targets except arm7_9 and mips, which
are the only ones with real implementations. Replace with a single default
implementation simply calling target_write_memory().

Change-Id: I9228104240bc0b50661be20bc7909713ccda2164
Signed-off-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>
Reviewed-on: http://openocd.zylin.com/1213
Tested-by: jenkins
Reviewed-by: Øyvind Harboe <oyvindharboe@gmail.com>
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>
target: Retire target_bulk_write_memory()

The only caller was arm_nandwrite(). Replace that call with
target_write_buffer() instead, which in turn may end up calling the same
bulk_write_memory target API function.

Change-Id: If34c7474df5cf14af3b732fb4774816818f28e79
Signed-off-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>
Reviewed-on: http://openocd.zylin.com/1214
Tested-by: jenkins
Reviewed-by: Øyvind Harboe <oyvindharboe@gmail.com>
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>