MIPS: math-emu: dsemul: Remove an unused bit in ADDIUPC emulation

Avoid a reader's confusion, as the calculation is correct either way.

Signed-off-by: Maciej W. Rozycki <macro@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/12283/


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