MIPS: r4kcache: Use correct base register for MIPS R6 cache flushes

Commit 934c7923("MIPS: asm: r4kcache: Add MIPS R6 cache unroll
functions") added support for MIPS R6 cache flushes but it used the
wrong base address register to perform the flushes so the same lines
were flushed over and over. Moreover, replace the "addiu" instructions
with LONG_ADDIU so the correct base address is calculated for 64-bit
cores.

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Fixes: 934c7923("MIPS: asm: r4kcache: Add MIPS R6 cache unroll functions")
Cc: linux-mips@linux-mips.org
Reviewed-by: Maciej W. Rozycki <macro@linux-mips.org>
Patchwork: https://patchwork.linux-mips.org/patch/9384/


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