Hack to fix broken OMAP dss build in linaro 2.6.39 tree.

[John Stultz]

So if the OMAP_DSS_DPI option is enabled, and the OMAP2_DSS_DSI option
is not, you get the following build error with Nico's tree:

drivers/video/omap2/dss/dpi.c: In function 'dpi_set_dsi_clk':
drivers/video/omap2/dss/dpi.c:61: error: implicit declaration of function 'dsi_pll_calc_clock_div_pck'
drivers/video/omap2/dss/dpi.c:66: error: implicit declaration of function 'dsi_pll_set_clock_div'
drivers/video/omap2/dss/dpi.c: In function 'omapdss_dpi_display_enable':
drivers/video/omap2/dss/dpi.c:192: error: implicit declaration of function 'dsi_pll_init'
drivers/video/omap2/dss/dpi.c:209: error: implicit declaration of function 'dsi_pll_uninit'
make[4]: *** [drivers/video/omap2/dss/dpi.o] Error 1

This was reported to the mailing list almost two weeks ago, and still is
unfixed. 

The following hack works around the issue by making sure DSI is enabled
if DPI is enabled. Although I suspect this fix would still break if
OMAP3 was disabled, but no worse then it already does today. 

Nico: Hopefully a proper fix is on its way, but in the meantime, please
consider merging this.

thanks
-john

Signed-off-by: John Stultz <john.stultz at linaro.org>

diff --git a/drivers/video/omap2/dss/Kconfig b/drivers/video/omap2/dss/Kconfig
index 7a49a75..ae472a1 100644
--- a/drivers/video/omap2/dss/Kconfig
+++ b/drivers/video/omap2/dss/Kconfig
@@ -38,6 +38,7 @@ config OMAP2_DSS_COLLECT_IRQ_STATS
 
 config OMAP2_DSS_DPI
 	bool "DPI support"
+	select OMAP2_DSS_DSI
 	default y
 	help
 	  DPI Interface. This is the Parallel Display Interface.