staging: fsl-mc:Added support for atomic portals

Refactored mc_send_command() to support two flavors of polling:
- preemptible (for non-atomic portals), which was already supported.
  It calls usleep_range() between polling iterations.
- non-preemptible (for atomic portals), which is needed when
  mc_send_command() is called with interrupts disabled.
  It calls udelay() between polling iterations.

Signed-off-by: J. German Rivera <German.Rivera@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>