Replace passive voice with active voice and other tweaks.

• Drop uses of 'will'.
• Replace 'to use' with active voice.
• Tidy language around interrupt types and clarify that INTx doesn't work on VFs.
• Drop leading articles from sysctl/tunable descriptions.
• Tweak the wording of several sysctl/tunable descriptions.

Submitted by: wblock (1, 2, 4)
Sponsored by: Chelsio Communications
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D8812