[mips][micromips] Fix how values in .gcc_except_table are calculated

When a landing pad is calculated in a program that is compiled
for micromips, it will point to an even address. Such an error will
cause a segmentation fault, as the instructions in micromips are
aligned on odd addresses. This patch sets the last bit of the offset
where a landing pad is, to 1, which will effectively be
an odd address and point to the instruction exactly.

Differential Revision: https://reviews.llvm.org/D52985

llvm-svn: 344591