elfload: Fix alignment when unmapping excess reservation

elfload: Fix alignment when unmapping excess reservation

When complying with the alignment requested in the ELF and unmapping
the excess reservation, having align_end not aligned to the guest page
causes the unmap to be rejected by the alignment check at
target_munmap and later brk adjustments hit an EEXIST.

Fix by aligning the start of region to be unmapped.

Fixes: c81d1fafa6 ("linux-user: Honor elf alignment when placing images")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1913
Signed-off-by: Fabiano Rosas <farosas@suse.de>
[rth: Align load_end as well.]
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20250213143558.10504-1-farosas@suse.de>
(cherry picked from commit 4b7b20a3b72c5000ea71bef505c16e6e628268b6)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>