memory: tegra: fix unused-function warning

The tegra186_mc_client_sid_override() is only called from
an #ifdef block:

drivers/memory/tegra/tegra186.c:74:13: error: 'tegra186_mc_client_sid_override' defined but not used [-Werror=unused-function]
   74 | static void tegra186_mc_client_sid_override(struct tegra_mc *mc,
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Add another #ifdef around the called function.

Fixes: 393d66fd ("memory: tegra: Implement SID override programming")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Jon Hunter <jonathanh@nvidia.com>
Link: https://lore.kernel.org/r/20210722090748.1157470-1-arnd@kernel.orgSigned-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>

drivers/memory/tegra/tegra186.c

@@ -71,6 +71,7 @@ static int tegra186_mc_resume(struct tegra_mc *mc)
 	return 0;
 }
 
+#if IS_ENABLED(CONFIG_IOMMU_API)
 static void tegra186_mc_client_sid_override(struct tegra_mc *mc,
 					    const struct tegra_mc_client *client,
 					    unsigned int sid)
@@ -108,6 +109,7 @@ static void tegra186_mc_client_sid_override(struct tegra_mc *mc,
 		writel(sid, mc->regs + client->regs.sid.override);
 	}
 }
+#endif
 
 static int tegra186_mc_probe_device(struct tegra_mc *mc, struct device *dev)
 {