Revert "build: Use filechk rules to create and update u-boot.lds"

This reverts commit a8b993eb81c142a439c24b871a2317f765fe5397.

Commit a8b993eb claims it fixes u-boot.lds rule by replacing
$(call if_changed) with $(call filechk).

But the problem had already been fixed by commit 395e60cd
a few days before commit a8b993eb was posted.

There is no reason to apply commit a8b993eb. What is worse is
$(call filechk) is too strong to fix the problem and looks weird.

Date of the two patches:

[1] commit 395e60cdc292dc0183c6867d34b43f14a373df55
    Author:     Masahiro Yamada <yamada.m@jp.panasonic.com>
    AuthorDate: Wed Apr 9 20:10:43 2014 +0900
    Commit:     Tom Rini <trini@ti.com>
    CommitDate: Fri Apr 11 10:08:42 2014 -0400
replaces $(call if_changed) -> $(call if_changed_dep)

[2] commit a8b993eb81c142a439c24b871a2317f765fe5397
    Author:     Jon Loeliger <jon.loeliger@oracle.com>
    AuthorDate: Tue Apr 15 16:09:37 2014 -0500
    Commit:     Tom Rini <trini@ti.com>
    CommitDate: Fri Apr 18 16:14:16 2014 -0400
replaces $(call if_changed) -> $(call filechk)

A conflict must have happened when applying [2], but somehow it was
applied, sadly.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Jon Loeliger <jon.loeliger@oracle.com>
Cc: Andreas Bießmann <andreas.devel@googlemail.com>
Cc: Tom Rini <trini@ti.com>