This is necessary to be able to include <linux/msi.h> when
CONFIG_GENERIC_MSI_IRQ_DOMAIN is enabled. Without this, a build with
CONFIG_GENERIC_MSI_IRQ_DOMAIN fails with:

   In file included from include/linux/kvm_host.h:20:0,
                    from arch/mips/kernel/asm-offsets.c:24:
>> include/linux/msi.h:197:10: fatal error: asm/msi.h: No such file or directory
    #include <asm/msi.h>
             ^~~~~~~~~~~
   compilation terminated.
   make[2]: *** [arch/mips/kernel/asm-offsets.s] Error 1
   make[2]: Target '__build' not remade because of errors.
   make[1]: *** [prepare0] Error 2
   make[1]: Target 'prepare' not remade because of errors.
   make: *** [sub-make] Error 2
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Patchwork: https://patchwork.linux-mips.org/patch/19986/
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Hanna Hawa <hannah@marvell.com>