firmware: tegra: bpmp: Drop unused mbox_client_to_bpmp()

mbox_client_to_bpmp() is not used, W=1 builds:

  drivers/firmware/tegra/bpmp.c:28:1: error: unused function 'mbox_client_to_bpmp' [-Werror,-Wunused-function]

Fixes: cdfa358b ("firmware: tegra: Refactor BPMP driver")
Cc: stable@vger.kernel.org
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/firmware/tegra/bpmp.c

@@ -24,12 +24,6 @@
 #define MSG_RING	BIT(1)
 #define TAG_SZ		32
 
-static inline struct tegra_bpmp *
-mbox_client_to_bpmp(struct mbox_client *client)
-{
-	return container_of(client, struct tegra_bpmp, mbox.client);
-}
-
 static inline const struct tegra_bpmp_ops *
 channel_to_ops(struct tegra_bpmp_channel *channel)
 {