board/riscv/nommu: bump kernel version and drop no longer needed patch

board/riscv/nommu: bump kernel version and drop no longer needed patch

Bump the kernel version for all riscv nommu configs from 5.18 to 5.19.
That way, we can remove the one and only riscv nommu patch,
since this patch is included in kernel 5.19.

Signed-off-by: Niklas Cassel <[email protected]>
Reviewed-by: Damien Le Moal <[email protected]>
Signed-off-by: Thomas Petazzoni <[email protected]>