MIPS: Print CM error reports upon bus errors

MIPS: Print CM error reports upon bus errors

If a bus error occurs on a system with a MIPS Coherence Manager (CM)
then the CM may hold useful diagnostic information. Printing this out
has so far been left up to boards, with the requirement that they
register a board_be_handler function & call mips_cm_error_decode() from
there.

In order to avoid boards other than Malta needing to duplicate this
code, call mips_cm_error_decode() automatically if the board registers
no board_be_handler, and remove the Malta implementation of that.

This patch results in no functional change, but removes a further piece
of platform-specific code.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14350/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>