Stack overflow gap size can be unaligned to a page

Remove the alignment assertions as there is no requirement
for the stack overflow gap size to be aligned to page size.

Test: Same as for I5430741a8494b340ed7fd2d8692c41a59ad9c530.
      The whole patches chain was tested as a whole.
Change-Id: Iac5e7ffb2f4690ee33bf4d1f3557c13ae7e5729f
1 file changed