Make the presence of Linux SPI headers mandatory for linux_spi

This solution is copied from ft2232_spi and is equally hacky.
Thanks to M.K. for investigating the history of <linux/spi/spidev.h>, which
led to a hopefully more robust check.

Corresponding to flashrom svn r1517.

Signed-off-by: Stefan Tauner <stefan.tauner@alumni.tuwien.ac.at>
Acked-by: Michael Karcher <flashrom@mkarcher.dialup.fu-berlin.de>
2 files changed