[mips] Fix JmpLink to texternalsym and tglobaladdr on mcroMIPS R6

[mips] Fix JmpLink to texternalsym and tglobaladdr on mcroMIPS R6

There is not match for the `MipsJmpLink texternalsym` and `MipsJmpLink
tglobaladdr` patterns for microMIPS R6. As a result LLVM incorrectly
selects the `JALRC16` compact 2-byte instruction which takes a target
instruction address from a register only and assign `R_MIPS_32` relocation
for this instruction. This relocation completely overwrites `JALRC16`
and nearby instructions.

This patch adds missed matching patterns, selects `BALC` instruction and
assign a correct `R_MICROMIPS_PC26_S1` relocation.

Differential Revision: https://reviews.llvm.org/D64552

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@365870 91177308-0d34-0410-b5e6-96231b3b80d8