clk: zynqmp: Add fallthrough statement in the switch case

clk: zynqmp: Add fallthrough statement in the switch case

Add fallthrough statement in switch case to fix the sparse warning.
In function 'zynqmp_clk_get_rate': warning: this statement may
fall through [-Wimplicit-fallthrough=]

Signed-off-by: Algapally Santosh Sagar <santoshsagar.algapally@amd.com>
Signed-off-by: Venkatesh Yadav Abbarapu <venkatesh.abbarapu@amd.com>
Link: https://lore.kernel.org/r/20230519113816.22083-2-venkatesh.abbarapu@amd.com
Signed-off-by: Michal Simek <michal.simek@amd.com>