RDMA/rtrs-clt: Replace list_next_or_null_rr_rcu with an inline function

removes list_next_or_null_rr_rcu macro to fix below warnings.
That macro is used only twice.
CHECK:MACRO_ARG_REUSE: Macro argument reuse 'head' - possible side-effects?
CHECK:MACRO_ARG_REUSE: Macro argument reuse 'ptr' - possible side-effects?
CHECK:MACRO_ARG_REUSE: Macro argument reuse 'memb' - possible side-effects?

Replaces that macro with an inline function.

Fixes: 6a98d71d ("RDMA/rtrs: client: main functionality")
Cc: jinpu.wang@ionos.com
Link: https://lore.kernel.org/r/20220712103113.617754-5-haris.iqbal@ionos.com


Signed-off-by: Md Haris Iqbal <haris.iqbal@ionos.com>
Suggested-by: Jason Gunthorpe <jgg@ziepe.ca>
Signed-off-by: Jack Wang <jinpu.wang@ionos.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>