zynqmp: pm: Return the buffered PLL mode through IOCTL PLL get mode API

zynqmp: pm: Return the buffered PLL mode through IOCTL PLL get mode API

When linux calls pm_ioctl_get_pll_frac_mode() it doesn't expect the actual
mode to be read from hardware, but the value that it is intending to
program. Therefore, we return the buffered value to linux.

Signed-off-by: Mirela Simonovic <mirela.simonovic@aggios.com>
Acked-by: Will Wong <WILLW@xilinx.com>
Signed-off-by: Jolly Shah <jollys@xilinx.com>