staging: lustre: lnet: use correct 'magic' test

Use the lnet_magic_accept() function to compare 'magic' against
LNET_PROTO_TCP_MAGIC for the appropriate string for an error message.

The original fix removed an unneeded byte-ordering cast because the define
was already CPU byte-ordered and it was assumed that 'magic' was CPU
byte-ordered, too.

Now modify the if-statement to use the appropriate lnet_accept_magic()
function in order to be consistent with similar tests. This will allow
the code to be consistent with the general understanding that 'magic'
should be in host-byte-order for the peer that sent the message.

Fixes: 80782927 ("staging: lustre: Fix unneeded byte-ordering cast")
Signed-off-by: Justin Skists <j.skists@gmail.com>
Reviewed-by: NeilBrown <neil@brown.name>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>