mmc: zynq_sdhci: Change granularity of timeout to 1us

The timeout used in 'commit b6f44082 ("mmc: zynq_sdhci: Wait
till sd card detect state is stable")' workaround is 1000ms at a
granularity of 1msec. Change it to 1usec, to not waste time incase the
cd is stable.

Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Link: https://lore.kernel.org/r/f008d2bcf864702a01564789f14f9cdecb8acd45.1645625609.git.michal.simek@xilinx.com