Enable parsing simple-bus 'ranges' with multiple entries

This patch makes possible to boot with up to 8 ranges in soc.
Dynamic allocation cannot be used, because ftd_get_ranges
function is called early, when malloc is not available.

Change is required for the alignment of Marvell Armada 38x
device trees present in sys/gnu/dts/arm - originally
the platform has 6 entries in simple-bus 'ranges'.

Submitted by: Patryk Duda <pdk@semihalf.com>
Reviewed by: manu, nwhitehorn, cognet (mentor)
Approved by: cognet (mentor)
Obtained from: Semihalf
Differential Revision: https://reviews.freebsd.org/D11876