uml: fix linker script alignment bugs

Fix a class of bugs in the UML linker scripts which caused section boundary
variables to sometimes not line up with their sections.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>