One of the interrupts in intel_vga_int15_handler lacks positive return status. Write correct status to avoid error messages in log. TEST=With this change `int15 call returned error` is not shown anymore on a custom board with Intel Atom CPU, i945GME northbridge and i82801gx southbridge. Change-Id: I740b2df9bd6a7d261d89bef74b924edbb64354aa Signed-off-by: Konstantin Aladyshev <aladyshev@nicevt.ru> Reviewed-on: http://review.coreboot.org/12255 Tested-by: build bot (Jenkins) Reviewed-by: Ronald G. Minnich <rminnich@gmail.com> Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net> Reviewed-by: Patrick Georgi <pgeorgi@google.com>