ARM: dts: imx8qm-apalis: replace dm-spl with dm-pre-proper

ARM: dts: imx8qm-apalis: replace dm-spl with dm-pre-proper

For non-SPL/TPL setups dm-spl, dm-tpl, dm-pre-proper, dm-pre-reloc are
handled equally, forcing the nodes with these properties
to be accessible and device being probed
before pre-relocation of U-Boot proper (drivers/core/util.c):

bool ofnode_pre_reloc(ofnode node)
{
    /* for SPL and TPL the remaining nodes after the fdtgrep 1st pass
     * had property dm-pre-reloc or u-boot,dm-spl/tpl.
     * They are removed in final dtb (fdtgrep 2nd pass)
     */
    return true;
    if (ofnode_read_bool(node, "u-boot,dm-pre-reloc"))
        return true;
    if (ofnode_read_bool(node, "u-boot,dm-pre-proper"))
        return true;

    /*
     * In regular builds individual spl and tpl handling both
     * count as handled pre-relocation for later second init.
     */
    if (ofnode_read_bool(node, "u-boot,dm-spl") ||
        ofnode_read_bool(node, "u-boot,dm-tpl"))
        return true;

    return false;
}

Howewer, to avoid confusion in future, replace dm-spl
`%s/dm-spl/dm-pre-proper/g` properties to dm-pre-proper
to explicitly state that they are handled during pre-relocation
stage of U-Boot proper.

Signed-off-by: Igor Opaniuk <igor.opaniuk@toradex.com>
Reviewed-by: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>