MIPS: Discard .eh_frame sections in linker script.

Some toolchains (including Cavium OCTEON SDK) are emitting .eh_frame
sections by default.  Discard them as they are useless in the kernel.

Signed-off-by: David Daney <david.daney@cavium.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/5684/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>