cd9660: Partial style sweep of Rock Ridge code

This mostly just fixes indentation and continuations and adds spaces
after commas and around binary operators and parentheses around return
values, but cd9660_rrip_extref() was so egregiously unreadable I
rewrote it. Note that this was done manually, so I may have missed a
few spots, and I made no attempt to fix over-long lines.

MFC after: 1 week
Reviewed by: markj
Differential Revision: https://reviews.freebsd.org/D55865