staging: mt7621-dts: make use of 'IRQ_TYPE_LEVEL_HIGH' instead of magic numbers

Nodes 'gdma' and 'hsdma' are using magic number '4' in interrupts property.
Use 'IRQ_TYPE_LEVEL_HIGH' instead to align with the rest of the nodes in
the file.

Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Link: https://lore.kernel.org/r/20211019102915.15409-2-sergio.paracuellos@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>