Tegra: Change Tegra20 to Tegra in common code, prep for T30

Convert TEGRA20_ defines to either TEGRA_ or NV_PA_ where appropriate.
Convert tegra20_ source file and function names to tegra_, also.

Upcoming Tegra30 port will use common code/defines/names where possible.

Signed-off-by: Tom Warren <twarren@nvidia.com>
Acked-by: Stephen Warren <swarren@nvidia.com>
diff --git a/board/nvidia/whistler/whistler.c b/board/nvidia/whistler/whistler.c
index c0a114d..598b2e5 100644
--- a/board/nvidia/whistler/whistler.c
+++ b/board/nvidia/whistler/whistler.c
@@ -81,10 +81,10 @@
 	pin_mux_mmc();
 
 	/* init dev 0 (SDMMC4), (J29 "HSMMC") with 8-bit bus */
-	tegra20_mmc_init(0, 8, -1, -1);
+	tegra_mmc_init(0, 8, -1, -1);
 
 	/* init dev 1 (SDMMC3), (J40 "SDIO3") with 8-bit bus */
-	tegra20_mmc_init(1, 8, -1, -1);
+	tegra_mmc_init(1, 8, -1, -1);
 
 	return 0;
 }