target-mips: correct the values in the DSP tests

Five tests files for DSP instructions had wrong expected values in the tests.
This change fixes this, and this has been cross-checked by running the same
test binaries on Malta 74K board.

Signed-off-by: Petar Jovanovic <petar.jovanovic@imgtec.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
