lib/tiny-printf.c: Add tiny printf function for space limited environments

This patch adds a small printf() version that supports all basic formats.
Its intented to be used in U-Boot SPL versions on platforms with very
limited internal RAM sizes.

To enable it, just define CONFIG_USE_TINY_PRINTF in your defconfig. This
will result in the SPL using this tiny function and the main U-Boot
still using the full-blown printf() function.

This code was copied from:
http://www.sparetimelabs.com/printfrevisited
With mostly only coding style related changes so that its checkpatch
clean.

The size reduction is about 2.5KiB. Here a comparison for the db-mv784mp-gp
(Marvell AXP) SPL:

Without this patch:
  58963   18536    1928   79427   13643 ./spl/u-boot-spl

With this patch:
  56542   18536    1956   77034   12cea ./spl/u-boot-spl

Note:
To make it possible to compile tiny-printf.c instead of vsprintf.c when
CONFIG_USE_TINY_PRINTF is defined, the functions printf() and vprintf() are
moved from common/console.c into vsprintf.c in this patch.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Simon Glass <sjg@chromium.org>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Tom Rini <trini@konsulko.com>
Cc: Albert Aribaud <albert.u.boot@aribaud.net>

lib/Makefile

@@ -80,7 +80,18 @@ obj-y += string.o
 obj-y += time.o
 obj-$(CONFIG_TRACE) += trace.o
 obj-$(CONFIG_LIB_UUID) += uuid.o
-obj-y += vsprintf.o
 obj-$(CONFIG_LIB_RAND) += rand.o
 
+ifdef CONFIG_SPL_BUILD
+# SPL U-Boot may use full-printf, tiny-printf or none at all
+ifdef CONFIG_USE_TINY_PRINTF
+obj-$(CONFIG_SPL_SERIAL_SUPPORT) += tiny-printf.o
+else
+obj-$(CONFIG_SPL_SERIAL_SUPPORT) += vsprintf.o
+endif
+else
+# Main U-Boot always uses the full printf support
+obj-y += vsprintf.o
+endif
+
 subdir-ccflags-$(CONFIG_CC_OPTIMIZE_LIBS_FOR_SPEED) += -O2