[MIPS] Disable gdb tests call_from_gdb and change_variable
[MIPS] Disable gdb tests call_from_gdb and change_variable

Two gdb tests are disabled for MIPS:

1. call_from_gdb, because gdb for MIPS executes inferior calls on stack
by default. When gdb is modified to execute inferior calls AT_ENTRY, the
test will pass.

2. change_variable, because LLVM does not generate code that reads the value
again from the stack which is an assumption for gdb (that changes copy of
the variable on stack).

BUG= run_gdb_call_from_gdb_test, run_gdb_change_variable_test for MIPS
TEST= run the aforementioned tests on MIPS-board

Review URL: https://codereview.chromium.org/120083003

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@12568 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client