[mips][mips16] Re-work the inline assembly stubs to work with IAS. NFC.

Summary:
Previously, we were inserting an InlineAsm statement for each line of the
inline assembly. This works for GAS but it triggers prologue/epilogue
emission when IAS is in use. This caused:
    .set noreorder
    .cpload $25
to be emitted as:
    .set push
    .set reorder
    .set noreorder
    .set pop
    .set push
    .set reorder
    .cpload $25
    .set pop
which led to assembler errors and caused the test to fail.

The whitespace-after-comma changes included in this patch are necessary to
match the output when IAS is in use.

Reviewers: vkalintiris

Subscribers: rkotler, llvm-commits, dsanders

Differential Revision: http://reviews.llvm.org/D13653

llvm-svn: 250895