staging: unisys: visorbus: Use CURRENT_FILE_PC in base postcode macro

Use CURRENT_FILE_PC directly in the POSTCODE_LINUX macro instead of
relying on passthrough macros to provide it.

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>