That way, data source address does not depend on any other unrelated change in
linker script.
This also fixes cases when .data input section is aligned on 8 bytes. The new
version does not provide any address for the output section so that it is
aligned to the strictest input section. The _data_loadaddr symbol will
always take this alignment into account.
This is needed even in plain C when 64 bit variable (e.g. long long int)
arithmetic is used. For example it is required when newlib is compiled with
--enable-newlib-io-long-long.
Conflicts:
lib/stm32/f1/libopencm3_stm32f1.ld
lib/stm32/f2/libopencm3_stm32f2.ld
