ixgbevf: Use smp_rmb rather than read_barrier_depends

ixgbevf: Use smp_rmb rather than read_barrier_depends

commit ae0c585d93dfaf923d2c7eb44b2c3ab92854ea9b upstream.

The original issue being fixed in this patch was seen with the ixgbe
driver, but the same issue exists with ixgbevf as well, as the code is
very similar. read_barrier_depends is not sufficient to ensure
loads following it are not speculatively loaded out of order
by the CPU, which can result in stale data being loaded, causing
potential system crashes.

Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Acked-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>