Breakage from ARM when building x86

Either this needs the headers fixing or should be protected by an ARM
config, not sure which

drivers/mfd/twl-core.c: In function ‘twl_probe’:
drivers/mfd/twl-core.c:1218:2: error: implicit declaration of function
‘irq_alloc_descs’ [-Werror=implicit-function-declaration]
drivers/mfd/twl-core.c:1226:2: error: implicit declaration of function
‘irq_domain_add_legacy’ [-Werror=implicit-function-declaration]
drivers/mfd/twl-core.c:1227:11: error: ‘irq_domain_simple_ops’ undeclared
(first use in this function) drivers/mfd/twl-core.c:1227:11: note: each
undeclared identifier is reported only once for each function it appears
in cc1: some warnings being treated as errors

make[2]: *** [drivers/mfd/twl-core.o] Error 1
make[1]: *** [drivers/mfd] Error 2