Documentation: update kbuild loadable modules goals & examples

	Note: In this example $(CONFIG_ISDN_PPP_BSDCOMP) evaluates to 'm'

	If a kernel module is built from several source files, you specify

	that you want to build a module in the same way as above.

	Kbuild needs to know which the parts that you want to build your

	module from, so you have to tell it by setting an

	$(<module_name>-objs) variable.

	that you want to build a module in the same way as above; however,

	kbuild needs to know which object files you want to build your

	module from, so you have to tell it by setting a $(<module_name>-y)

	variable.

	Example:

		#drivers/isdn/i4l/Makefile

		obj-$(CONFIG_ISDN) += isdn.o

		isdn-objs := isdn_net_lib.o isdn_v110.o isdn_common.o

		obj-$(CONFIG_ISDN_I4L) += isdn.o

		isdn-y := isdn_net_lib.o isdn_v110.o isdn_common.o

	In this example, the module name will be isdn.o. Kbuild will

	compile the objects listed in $(isdn-objs) and then run

	compile the objects listed in $(isdn-y) and then run

	"$(LD) -r" on the list of these files to generate isdn.o.

	Kbuild recognises objects used for composite objects by the suffix

	-objs, and the suffix -y. This allows the Makefiles to use

	the value of a CONFIG_ symbol to determine if an object is part

	of a composite object.

	Due to kbuild recognizing $(<module_name>-y) for composite objects,

	you can use the value of a CONFIG_ symbol to optionally include an

	object file as part of a composite object.

	Example:

		#fs/ext2/Makefile

	        obj-$(CONFIG_EXT2_FS) += ext2.o

		ext2-y                       := balloc.o bitmap.o

	        ext2-$(CONFIG_EXT2_FS_XATTR) += xattr.o

	In this example, xattr.o is only part of the composite object

	ext2.o if $(CONFIG_EXT2_FS_XATTR) evaluates to 'y'.

		ext2-y := balloc.o dir.o file.o ialloc.o inode.o ioctl.o \

			  namei.o super.o symlink.o

	        ext2-$(CONFIG_EXT2_FS_XATTR) += xattr.o xattr_user.o \

						xattr_trusted.o

	In this example, xattr.o, xattr_user.o and xattr_trusted.o are only

	part of the composite object ext2.o if $(CONFIG_EXT2_FS_XATTR)

	evaluates to 'y'.

	Note: Of course, when you are building objects into the kernel,

	the syntax above will also work. So, if you have CONFIG_EXT2_FS=y,