Fix unit tests for TEST_ASSERT_EQUAL_HEX_ARRAY on 16-bit architectures

Previously, TEST_ASSERT_EQUAL_HEX_ARRAY was being called, and passed
arrays of type 'unsigned int'. TEST_ASSERT_EQUAL_HEX_ARRAY is an alias
for TEST_ASSERT_EQUAL_HEX32_ARRAY in *all* cases (and is documented as
such), while 'unsigned int' is 16 bits on some platforms. Unsurprisingly
this caused some tests to fail.

Fix by replacing the 'unsigned int' declarations with '_UU32'.