mips: Remove obsolete configs IRQ_MSP_CIC and IRQ_MSP_SLP

Commit 1b00767f ("MIPS: Remove PMC MSP71xx platform") removes all uses
of the config IRQ_MSP_CIC and IRQ_MSP_SLP.

Remove these two obsolete configs IRQ_MSP_CIC and IRQ_MSP_SLP.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>