msadp32: Do not enumerate 8bit PCM formats, they cannot be converted.

[Joerg-Cyril.Hoehle at t-systems.com]

>> I found it illogical to advertise unusable 8bit formats. But 
>>I did not cross check whether MS-Windows would do so.
Indeed, MS-Windows advertises both 8 and 16 bit formats.
Jeff Zaroyko kindly supplied me with winetest results ran with
WINETEST_INTERACTIVE=1 on MS-Windows Vista.  The msacm test
then displays all advertised formats.

However I've not tested whether MS-Windows actually converts the
advertised 8 bit formats.

Regards,
	Jorg Hohle