elf: Properly align PT_LOAD segments [BZ #28676]

When PT_LOAD segment alignment > the page size, allocate enough space to
ensure that the segment can be properly aligned.  This change helps code
segments use huge pages become simple and available.

This fixes [BZ #28676].

Signed-off-by: Xu Yu <xuyu@linux.alibaba.com>
Signed-off-by: Rongwei Wang <rongwei.wang@linux.alibaba.com>