Revert "pcm_native.c: remove unused label"

This reverts commit 680db0136e0778a0d7e025af7572c6a8d82279e2.  The label
is actually used, but hidden behind CONFIG_SND_DEBUG and the horrible
snd_assert() macro.

That macro could probably be improved to be along the lines of

	#define snd_assert(expr, args...) do { if ((void)(expr),0) { args; } } while (0)

or similar to make sure that we always both evaluate 'expr' and parse
'args', but while gcc should optimize it all away, I'm too lazy to
really verify that.  So I'll just admit defeat and will continue to live
with the annoying warning.

Noted-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: Linus "Grr.." Torvalds