common: Add symbol handling for generic lists into Makefile

This patch adds essential components for generation of the contents of
the linker section that is used by the linker-generated array. All of
the contents is held in a separate file, u-boot.lst, which is generated
at runtime just before U-Boot is linked.

The purpose of this code is to especially generate the appropriate
boundary symbols around each subsection in the section carrying the
linker-generated arrays. Obviously, the interim linker code for actual
placement of the variables into the section is generated too. The
generated file, u-boot.lst, is included into u-boot.lds via the linker
INCLUDE directive in u-boot.lds .

Adjustments are made in the Makefile and spl/Makefile so that the
u-boot.lds and u-boot-spl.lds depend on their respective .lst files.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Joe Hershberger <joe.hershberger@gmail.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
Tested-by: Joe Hershberger <joe.hershberger@ni.com>