Revert "Staging: panel: usleep_range is preferred over udelay"

Revert "Staging: panel: usleep_range is preferred over udelay"

This reverts commit 38201f4a02b593530e24658978d3c393fbcc741a.

We should not be sleeping inside spin_lock.

Fixes: 38201f4a02b5 ("Staging: panel: usleep_range is preferred over udelay")
Cc: Sirnam Swetha <theonly.ultimate@gmail.com>
Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org>
Reported-by: Huang, Ying <ying.huang@intel.com>
Tested-by: Huang, Ying <ying.huang@intel.com>
Cc: stable <stable@vger.kernel.org> # 4.4
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>