net/smc: fix documentation of buffer sizes

Since commit 833bac7e ("net/smc: Fix setsockopt and sysctl to
specify same buffer size again") the SMC protocol uses its own
default values for the smc.rmem and smc.wmem sysctl variables
which are no longer derived from the TCP IPv4 buffer sizes.

Fixup the kernel documentation to reflect this change, too.

Fixes: 833bac7e ("net/smc: Fix setsockopt and sysctl to specify same buffer size again")
Signed-off-by: Gerd Bayer <gbayer@linux.ibm.com>
Reviewed-by: Wenjia Zhang <wenjia@linux.ibm.com>
Reviewed-by: Dust Li <dust.li@linux.alibaba.com>
Link: https://lore.kernel.org/r/20231030170343.748097-1-gbayer@linux.ibm.com


Signed-off-by: Paolo Abeni <pabeni@redhat.com>