[IA64] Fix build breakage - sn_force_interrupt_flag: undefined
[IA64] Fix build breakage - sn_force_interrupt_flag: undefined

Latest irq changes removed the need for this forcing flag, and the
definition - but missed the code that allowed it to be tweaked via
/proc.  Delete accessor functions too.

Signed-off-by: Tony Luck <e7984595ec0368ff920a7b3521dc7093683f6f26@intel.com>

KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs