Use gic_decode_fdt() rather than a local routine to parse fdt interrupt
properties.  Move fdt_pic_table and fdt_fixup_table into imx6_machdep.c,
which means imx6 doesn't need imx_common.c anymore.


git-svn-id: svn+ssh://svn.freebsd.org/base/head@271607 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f