clk: zynqmp: Add support for enabling clock on lpd_lsbus

lpd_lsbus is clock which is used by many IPs like dmas, gems, gpio, sdhcis,
spis, ttcs, uarts, watchdog that's why make sense to also enable access to
change this clock. For this clock you already get the rate.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>