firmware: imx: Add stub functions for SCMI LMM API

To ensure successful builds when CONFIG_IMX_SCMI_LMM_DRV is not enabled,
this patch adds static inline stub implementations for the following
functions:

  - scmi_imx_lmm_operation()
  - scmi_imx_lmm_info()
  - scmi_imx_lmm_reset_vector_set()

These stubs return -EOPNOTSUPP to indicate that the functionality is not
supported in the current configuration. This avoids potential build or
link errors in code that conditionally calls these functions based on
feature availability.

Fixes: 7242bbf ("firmware: imx: Add i.MX95 SCMI LMM driver")
Reviewed-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

Author: MrVan

include/linux/firmware/imx/sm.h

@@ -56,7 +56,24 @@ enum scmi_imx_lmm_op {
 #define SCMI_IMX_LMM_OP_FORCEFUL	0
 #define SCMI_IMX_LMM_OP_GRACEFUL	BIT(0)
 
+#if IS_ENABLED(CONFIG_IMX_SCMI_LMM_DRV)
 int scmi_imx_lmm_operation(u32 lmid, enum scmi_imx_lmm_op op, u32 flags);
 int scmi_imx_lmm_info(u32 lmid, struct scmi_imx_lmm_info *info);
 int scmi_imx_lmm_reset_vector_set(u32 lmid, u32 cpuid, u32 flags, u64 vector);
+#else
+static inline int scmi_imx_lmm_operation(u32 lmid, enum scmi_imx_lmm_op op, u32 flags)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int scmi_imx_lmm_info(u32 lmid, struct scmi_imx_lmm_info *info)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int scmi_imx_lmm_reset_vector_set(u32 lmid, u32 cpuid, u32 flags, u64 vector)
+{
+	return -EOPNOTSUPP;
+}
+#endif
 #endif