spi: Fix merge conflicts - Makefile

The patch "spi: tegra2: rename tegra2_spi.* to tegra_spi.*"
(sha1: edffa63d)
renamed tegra2_spi.c to tegra_spi.c

and the patch "Merge branch 'master' of git://git.denx.de/u-boot-microblaze

"
(sha1: d978780b)

has wrongly resolved confict.

This patch fix it.

Signed-off-by: Michal Simek <monstr@monstr.eu>