MIPS: kernel: entry.S: Set correct ISA level for mips_ihb

MIPS: kernel: entry.S: Set correct ISA level for mips_ihb

Commit 6ebb496ffc7e("MIPS: kernel: entry.S: Add MIPS R6 related
definitions") added the MIPSR6 definition but it did not update the
ISA level of the actual assembly code so a pre-MIPSR6 jr.hb instruction
was generated instead. Fix this by using the MISP_ISA_LEVEL_RAW macro.

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Fixes: 6ebb496ffc7e("MIPS: kernel: entry.S: Add MIPS R6 related definitions")
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9386/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>