staging: unisys: visorbus: Remove POSTCODE_LINUX_4 macro

Call POSTCODE_LINUX directly instead of passing through POSTCODE_LINUX_4.

Signed-off-by: Bryan Thompson <bryan.thompson@unisys.com>
Signed-off-by: David Kershner <david.kershner@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>