Minor refactor of N1 Mode Setting

-Replace discrete booleans with a set of integer
 to prepare for further expansion.
-Invert the logic from allowed reasons to disallowed
 reasons.

Note: refactor only; no functional change

Bug: 312788638
Test: atest GsmCdmaPhoneTest #no functional change
Test: Telephony Sanity (voice, data, sms) on Fi
Change-Id: I8e06d5d7e2afcc1bc41f7cd277d9424135d34b8c