clk: zynqmp: handle fixed factor param query error

Return proper error code in case query for fixed factor
parameter fails. This also fixes build warning for set
but not used variable 'ret'.

Signed-off-by: Rajan Vaja <rajan.vaja@xilinx.com>
Fixes: 3fde0e16 ("drivers: clk: Add ZynqMP clock driver")
Signed-off-by: Stephen Boyd <sboyd@kernel.org>