spi: xlp: Remove Netlogic XLP variants

spi: xlp: Remove Netlogic XLP variants

Netlogic XLP was removed in commit 6f736d15361a ("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.

Cc: Mark Brown <broonie@kernel.org>
Cc: linux-spi@vger.kernel.org
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20211109161325.2203564-1-robh@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>