[LLDB][MIPS] Adding call to IsMSAAvailable() while creating RegisterInfoInterface

This patch will fix the test case test_p_returns_correct_data_size_for_each_qRegisterInfo_attach_llgs_* of TestLldbGdbServer.py on mips. The test fails because we were sending RegisterInfo for msa registers to client even when msa registers are not available. With this commit server will send E45(end of resigters) response if msa registers are not available.

llvm-svn: 255108