elf2dmp: Rename PAGE_SIZE to ELF2DMP_PAGE_SIZE

elf2dmp: Rename PAGE_SIZE to ELF2DMP_PAGE_SIZE

As per POSIX specification of limits.h [1], OS libc may define
PAGE_SIZE in limits.h.

To prevent collosion of definition, we rename PAGE_SIZE here.

[1]: https://pubs.opengroup.org/onlinepubs/7908799/xsh/limits.h.html

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20210118063808.12471-6-jiaxun.yang@flygoat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>