MdeModulePkg/UefiBootManagerLib: Put BootMenu at the end of BootOrder

MdeModulePkg/UefiBootManagerLib: Put BootMenu at the end of BootOrder

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=3135

When Boot Menu does not exist in the BootOrder, BmRegisterBootManagerMenu
will create one into list. However, it should be put at the "end" of
BootOrder instead of "start" of BootOrder. Replace 0 by -1 to adjust
order of load options.

Signed-off-by: Walon Li <walon.li@hpe.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>