i2c: Remove Netlogic XLP variant

Netlogic XLP was removed in commit 95b8a5e0 ("MIPS: Remove NETLOGIC
support"). With those gone, the single platform left to support is
Cavium ThunderX2. Remove the Netlogic variant and DT support.

For simplicity, the existing kconfig name is retained.

Signed-off-by: Rob Herring <robh@kernel.org>
Acked-by George Cherian <gcherian@marvell.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>