rds: Fix endianness annotation of jhash wrappers

rds: Fix endianness annotation of jhash wrappers

__ipv6_addr_jhash (wrapper around jhash2()) and __inet_ehashfn (wrapper
around jhash_3words()) work with u32 (host endian) values but accept big
endian inputs. Declare the local variables as big endian to avoid
unnecessary casts.

Flagged by Sparse.

Signed-off-by: Ujwal Kundur <ujwal.kundur@gmail.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Link: https://patch.msgid.link/20250820175550.498-3-ujwal.kundur@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>