tegra: Indicate that binman makes all three output files

Use GNU make pattern rules to indicate that a single run of binman
produces all three Tegra output files. The avoids make running binman
three times (perhaps in parallel) and those instances inteferring with
each other.

See http://patchwork.ozlabs.org/patch/944611/ for the bug report.
Signed-off-by: NSimon Glass <sjg@chromium.org>
Tested-by: NStephen Warren <swarren@nvidia.com>

Makefile

@@ -1234,8 +1234,9 @@ endif
 
 ifneq ($(CONFIG_TEGRA),)
 ifneq ($(CONFIG_BINMAN),)
-u-boot-dtb-tegra.bin u-boot-tegra.bin u-boot-nodtb-tegra.bin: \
-		spl/u-boot-spl u-boot.bin FORCE
+# Makes u-boot-dtb-tegra.bin u-boot-tegra.bin u-boot-nodtb-tegra.bin
+%-dtb-tegra.bin %-tegra.bin %-nodtb-tegra.bin: \
+		spl/%-spl %.bin FORCE
 	$(call if_changed,binman)
 else
 OBJCOPYFLAGS_u-boot-nodtb-tegra.bin = -O binary --pad-to=$(CONFIG_SYS_TEXT_BASE)