sound: Expose EQ by default

The dev.pcm.%d.eq* sysctls and mixer "bass" and "treble" controls are
exposed only if hint.pcm.%d.eq is set. However, there is no good reason
why we shouldn't at least expose the controls, and let the user
enable/disable/bypass equalization through the sysctl.

Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Pull Request:	https://ron-dev.freebsd.org/FreeBSD/src/pulls/15

share/man/man4/pcm.4

@@ -197,9 +197,6 @@ The Parametric Software Equalizer (EQ) enables the use of
 controls (bass and treble).
 Commonly used for ear-candy or frequency compensation due to the vast
 difference in hardware quality.
-EQ is disabled by default, but can be enabled with the
-.Va hint.pcm.%d.eq
-tunable.
 .Ss VCHANs
 Each device can optionally support more playback and recording channels
 than physical hardware provides by using
@@ -230,12 +227,6 @@ driver.
 The following tunables can not be changed during runtime using
 .Xr sysctl 8 .
 .Bl -tag -width indent
-.It Va hint.pcm.%d.eq
-Set to 1 or 0 to explicitly enable (1) or disable (0) the equalizer.
-Requires a driver reload if changed.
-Enabling this will make bass and treble controls appear in mixer applications.
-This tunable is undefined by default.
-Equalizing is disabled by default.
 .It Va hint.pcm.%d.vpc
 Set to 1 or 0 to explicitly enable (1) or disable (0) the VPC feature.
 This tunable is undefined by default.