crypto: picoxcell - add dependency on HAVE_CLK

The picoxcell crypto driver requires the clk API, but the platform in
mainline does not currently support it.  Add an explicit dependency on
HAVE_CLK to avoid build breakage.

Signed-off-by: Jamie Iles <jamie@jamieiles.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>