MIPS: Module: Deal with malformed HI16/LO16 relocation sequences.

In case a series of R_MIPS_HI16 relocations was not followed by an
R_MIPS_LO16 relocation we were leaking the hi16 relocation chain.
Handle that error and return an error.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>