clk: ti: dra7: return error code in failure case

Add a returned error code in the MAX_APLL_WAIT_TRIES case.  Remove the
updating of the return variable r to 0 if MAX_APLL_WAIT_TRIES is not yet
reached, because r is already 0 at this point.

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Tero Kristo <t-kristo@ti.com>