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/arch/arm/include/asm/arch-tegra20/tegra_spi.h b/arch/arm/include/asm/arch-tegra20/tegra_spi.h
index 8978bea..d53a93f 100644
--- a/arch/arm/include/asm/arch-tegra20/tegra_spi.h
+++ b/arch/arm/include/asm/arch-tegra20/tegra_spi.h
@@ -70,6 +70,6 @@
 #define SPI_STAT_CUR_BLKCNT		(1 << 15)
 
 #define SPI_TIMEOUT		1000
-#define TEGRA20_SPI_MAX_FREQ	52000000
+#define TEGRA_SPI_MAX_FREQ	52000000
 
 #endif	/* _TEGRA_SPI_H_ */