net: designware: Invalidate RX buffer cache before freeing the DMA descriptor

In IPv6 context, the ICMP and UDP checksum byte in the RX packet
is initially set to 0, recaclculated, and then re-inserted.
This process can result in a dirty cache line. To prevent issues,
it is essential to invalidate cache for the RX buffer before freeing
the descriptor for next DMA transfer.
This ensure that the dirty cache line doesn't inadvertently written back
due to cache eviction, there by corrupting the RX buffer

Signed-off-by: Parvathi Bhogaraju <pbhogaraju@microsoft.com>
Signed-off-by: Jim Liu <JJLIU0@nuvoton.com>