Staging: mt29f_spinand: Replace udelay function with usleep_range

Use 'usleep_range' instead of 'udelay' to elapse time. For
spinand_reset, define the upper limit by a factor of 2 to keep the wait
short while still allowing a "good enough" range for wakeup. Define the
range 250us - 1ms for spinand_cmdfunc to provide enough leeway before
issuing spinand_reset. Checkpatch found this issue.

CHECK: usleep_range is preferred over udelay; see
Documentation/timers/timers-howto.txt

Signed-off-by: Eva Rachel Retuya <eraretuya@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>