MIPS: Move cache setup to setup_arch().

commit 97ce2c88f9ad42e3c60a9beb9fca87abf3639faa (jump-label: initialize
jump-label subsystem much earlier) breaks MIPS.  The jump_label_init()
call was moved before trap_init() which is where we initialize
flush_icache_range().

In order to be good citizens, we move cache initialization earlier so
that we don't jump through a null flush_icache_range function pointer
when doing the jump label initialization.

Signed-off-by: David Daney <david.daney@cavium.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/3822/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>