Unify interrupts bit definition and usage. While here remove PSR_C_bit.

Submitted by:	Svatopluk Kraus <onwahe at gmail.com>,
		Michal Meloun <meloun at miracle.cz>
Differential Revision: https://reviews.freebsd.org/D754


git-svn-id: svn+ssh://svn.freebsd.org/base/head@271398 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f