RDMA/vmw_pvrdma: Remove unused pvrdma_modify_device

RDMA/vmw_pvrdma: Remove unused pvrdma_modify_device

pvrdma_modify_device() was added in 2016 as part of
commit 29c8d9eba550 ("IB: Add vmw_pvrdma driver")
but accidentally it was never wired into the device_ops struct.

After some discussion the best course seems to be just to remove it,
see discussion at:
https://lore.kernel.org/all/Z8TWF6coBUF3l_jk@gallifrey/

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Link: https://patch.msgid.link/20250304215637.68559-1-linux@treblig.org
Acked-by: Vishnu Dasa <vishnu.dasa@broadcom.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>