ARM: remove dummy entries from .so init_array/fini_array

The runtime linker parses the ELF section headers to
discover the size of the init_array and fini_array, so
there is no point in putting NULL terminators at the end.

Change-Id: I3246cd585efce9314155600277dd829e9f37d04f
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@gmail.com>