tests: Added MIPS ISA test to learning_gem5/part1_tests.py

Running these tests on the MIPS ISA was part of the old scons-based
scripts and was not present in the Python testlib framework (those
executed via `tests/main.py`). This has been migrated.

Jira: https://gem5.atlassian.net/browse/GEM5-109
Change-Id: Id87022e99ea83768710fb96b55136f777182fd43
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/25803
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>

tests/gem5/learning_gem5/part1_test.py

@@ -33,7 +33,7 @@ gem5_verify_config(
     verifiers = (),
     config=joinpath(config_path, 'simple.py'),
     config_args = [],
-    valid_isas=('X86', 'RISCV', 'ARM'),
+    valid_isas=('X86', 'RISCV', 'ARM', 'MIPS'),
 )
 
 gem5_verify_config(
@@ -41,6 +41,6 @@ gem5_verify_config(
     verifiers = (),
     config=joinpath(config_path, 'two_level.py'),
     config_args = [],
-    valid_isas=('X86', 'RISCV', 'ARM'),
+    valid_isas=('X86', 'RISCV', 'ARM', 'MIPS'),
 )