MIPS: Remove clang-format-off from assembler tests.

Per request in https://codereview.chromium.org/1047213002/

These files will continue to have a lot of churn in next two months
as we finish support for MIPS r6 instruction set. When things settle
down, we will do a clang-format --full to clean them up. For now,
we'd prefer to be able to do easy diffs, and will do incremental
re-formats as we make changes.

BUG=

Review URL: https://codereview.chromium.org/1546973003

Cr-Commit-Position: refs/heads/master@{#33038}

test/cctest/test-assembler-mips.cc

@@ -47,8 +47,6 @@ typedef Object* (*F1)(int x, int p1, int p2, int p3, int p4);
 typedef Object* (*F2)(int x, int y, int p2, int p3, int p4);
 typedef Object* (*F3)(void* p, int p1, int p2, int p3, int p4);
 
-// clang-format off
-
 
 #define __ assm.
 

test/cctest/test-assembler-mips64.cc

@@ -47,8 +47,6 @@ typedef Object* (*F2)(int x, int y, int p2, int p3, int p4);
 typedef Object* (*F3)(void* p, int p1, int p2, int p3, int p4);
 typedef Object* (*F4)(int64_t x, int64_t y, int64_t p2, int64_t p3, int64_t p4);
 
-// clang-format off
-
 
 #define __ assm.