module: set .init_array alignment to 8

The proper idiom for aligning linker sections in modules is different
than for built-in sections.  ". = ALIGN();" followed by a forced
output address of 0 does nothing, as forcing the address changes the
value of ".".

Use output section alignment specifier instead.

Fixes: 9ddf8252 ("kernel: add support for .init_array.* constructors")
Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: David Daney <david.daney@cavium.com>
Signed-off-by: Jessica Yu <jeyu@redhat.com>