ALSA: core: Fix unexpected error at replacing user TLV

ALSA: core: Fix unexpected error at replacing user TLV

commit 88c54cdf61f508ebcf8da2d819f5dfc03e954d1d upstream.

When user tries to replace the user-defined control TLV, the kernel
checks the change of its content via memcmp().  The problem is that
the kernel passes the return value from memcmp() as is.  memcmp()
gives a non-zero negative value depending on the comparison result,
and this shall be recognized as an error code.

The patch covers that corner-case, return 1 properly for the changed
TLV.

Fixes: 8aa9b586e420 ("[ALSA] Control API - more robust TLV implementation")
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>