samples: move auxdisplay example code from Documentation

Move auxdisplay examples to samples and remove it from Documentation
Makefile. Create a new Makefile to build auxdisplay. It can be built
from top level directory or from auxdisplay directory:

Run make -C samples/auxdisplay or cd samples/auxdisplay; make

Acked-by: Jonathan Corbet <[e-mail]>
Signed-off-by: Shuah Khan <[e-mail]>

Documentation/Makefile

···
-subdir-y := accounting auxdisplay blackfin \
+subdir-y := accounting blackfin \
 	laptops pcmcia

Documentation/auxdisplay/Makefile

···
-# List of programs to build
-hostprogs-y := cfag12864b-example
-
-# Tell kbuild to always build the programs
-always := $(hostprogs-y)
-
-HOSTCFLAGS_cfag12864b-example.o += -I$(objtree)/usr/include

Documentation/auxdisplay/cfag12864b

···
 Also, you can mmap the framebuffer: open & mmap, munmap & close...
 which is the best option for most uses.
 
-Check Documentation/auxdisplay/cfag12864b-example.c
+Check samples/auxdisplay/cfag12864b-example.c
 for a real working userspace complete program with usage examples.

samples/auxdisplay/Makefile

···
+CC := $(CROSS_COMPILE)gcc
+CFLAGS := -I../../usr/include
+
+PROGS := cfag12864b-example
+
+all: $(PROGS)
+
+clean:
+	rm -fr $(PROGS)