sound: Remove obsolete DV_F_* flags

The ISA sound drivers that used them are retired.

Last reference of DV_F_DRQ_MASK and DV_F_DUAL_DMA:
716924cb4832ea0a440daf09913a06f3166f243e ("Retire snd_sbc ISA sound card
driver")

Last reference of DV_F_DEV_MASK and DV_F_DEV_SHIFT:
5126e5eeeb5e07ceef3c809452a8c9f508b2d4d1 ("Retire snd_mss ISA sound card
driver")

Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Reviewed by: markj, emaste
Differential Revision: https://reviews.freebsd.org/D44858