[PATCH] net/sunrpc/svcsock.c: fix a check

The return value of kernel_recvmsg() should be assigned to "err", not
compared with the random value of a never initialized "err" (and the "< 0"
check wrongly always returned false since == comparisons never have a
result < 0).

Spotted by the Coverity checker.

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Acked-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>