[llvm-readobj][ELF] Show MIPS GOT content when there is another zero-sized...

[llvm-readobj][ELF] Show MIPS GOT content when there is another zero-sized section at the same address

It is possible to have .got section and one or more zero-sized section
at the same address. This patch first checks that GOT (or GOT PLT)
section should have non-zero size using corresponding dynamic tags. Then
it looks up not empty section at the specified address.

Differential Revision: http://reviews.llvm.org/D16968

llvm-svn: 260245