staging: unisys: iovmcall_gnuc.h change -1 return values

This patch changes the vague -1 return values to -EPERM.
This operation is not supported is a good alternative
to -1 because the return is basically telling the caller
that the processor doesn't support vmcall operations.

Signed-off-by: Erik Arfvidson <erik.arfvidson@unisys.com>
Signed-off-by: David Kershner <david.kershner@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>