SUNRPC: Refactor gssx_dec_option_array() to kill uninitialized warning

net/sunrpc/auth_gss/gss_rpc_xdr.c: In function ‘gssx_dec_option_array’:
net/sunrpc/auth_gss/gss_rpc_xdr.c:258: warning: ‘creds’ may be used uninitialized in this function

Return early if count is zero, to make it clearer to the compiler (and the
casual reviewer) that no more processing is done.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>