MIPS: IRQ Stack: Fix erroneous jal to plat_irq_dispatch

Commit dda45f70 ("MIPS: Switch to the irq_stack in interrupts")
changed both the normal and vectored interrupt handlers. Unfortunately
the vectored version, "except_vec_vi_handler", was incorrectly modified
to unconditionally jal to plat_irq_dispatch, rather than doing a jalr to
the vectored handler that has been set up. This is ok for many platforms
which set the vectored handler to plat_irq_dispatch anyway, but will
cause problems with platforms that use other handlers.

Fixes: dda45f70 ("MIPS: Switch to the irq_stack in interrupts")
Signed-off-by: Matt Redfearn <matt.redfearn@imgtec.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/15110/Signed-off-by: James Hogan <james.hogan@imgtec.com>

arch/mips/kernel/genex.S

@@ -329,7 +329,7 @@ NESTED(except_vec_vi_handler, 0, sp)
 	PTR_ADD sp, t0, t1
 
 2:
-	jal	plat_irq_dispatch
+	jalr	v0
 
 	/* Restore sp */
 	move	sp, s1