target-i386: add API to get dump info

Dump info contains: endian, class and architecture. The next
patch will use these information to create vmcore. Note: on
x86 box, the  class is ELFCLASS64 if the memory is larger than 4G.

Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>