mmc: zynq_sdhci: Make variables/structure static

All these variables/structure are local and should be static.

Issues are reported by sparse:
drivers/mmc/zynq_sdhci.c:49:11: warning: symbol 'zynqmp_iclk_phases' was not declared. Should it be static?
drivers/mmc/zynq_sdhci.c:50:11: warning: symbol 'zynqmp_oclk_phases' was not declared. Should it be static?
drivers/mmc/zynq_sdhci.c:53:11: warning: symbol 'versal_iclk_phases' was not declared. Should it be static?
drivers/mmc/zynq_sdhci.c:54:11: warning: symbol 'versal_oclk_phases' was not declared. Should it be static?
drivers/mmc/zynq_sdhci.c:546:24: warning: symbol 'arasan_ops' was not declared. Should it be static?

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma@xilinx.com>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>