MIPS: MSP71xx: Remove compilation error when CONFIG_MIPS_MT is present

MIPS: MSP71xx: Remove compilation error when CONFIG_MIPS_MT is present

When CONFIG_MIPS_MT is defined, code is enabled that tries to call
'set_vi_handler()'. This function is declared in <asm/setup.h> but the
header is never included. Therefore, the compilation breaks.

arch/mips/pmcs-msp71xx/msp_irq.c:133: error: implicit declaration of function 'set_vi_handler'

This error was found with vampyr.

Signed-off-by: Stefan Hengelein <stefan.hengelein@fau.de>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Cc: ryazanov.s.a@gmail.com
Patchwork: https://patchwork.linux-mips.org/patch/8122/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>