arm: mach-k3: am62: move device identification accessor functions to header

mach-k3/am625_fdt.c does fdt fixup depending on fields in the device
identification register. Move the accessors to the device identification
register as inline functions into the am62_hardware.h header, so that
they can be used for other functionality.

Signed-off-by: Max Krummenacher <max.krummenacher@toradex.com>