sound: virtuoso: revert "do not overwrite EEPROM on Xonar D2/D2X"

This reverts commit 7e86c0e6 ("do not
overwrite EEPROM on Xonar D2/D2X") because it did not actually help with
the problem.

More user reports show that the overwriting of the EEPROM is not
triggered by using this driver but by installing Linux, and that the
installation of any other operating system (even one without any CMI8788
driver) has the same effect.  In other words, the presence of this
driver does not have any effect on the occurrence of the error.  (So
far, the available evidence seems to point to a BIOS bug.)

Furthermore, it turns out that the EEPROM chip is protected against
stray write commands by the command format and by requiring a separate
write-enable command, so the error scenario in the previous commit (that
SPI writes can be misinterpreted as an EEPROM write command) is not even
theoretically possible.

The mixer control that was removed as a consequence of the previous
commit can only be partially emulated in userspace, which also means it
cannot be seen be the in-kernel OSS API emulation, so it is better to
revert that change.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Cc: <stable@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>