SPM: Update log parameter to 'char *'

As the log message is expected to be standard ASCII characters.

Change-Id: Ia4b898df7e7c8dae20cffec189c8669c8f49b970
Signed-off-by: Shawn Shan <Shawn.Shan@arm.com>
diff --git a/platform/ext/common/tfm_hal_spm_logdev.h b/platform/ext/common/tfm_hal_spm_logdev.h
index 9715263..35f9a18 100644
--- a/platform/ext/common/tfm_hal_spm_logdev.h
+++ b/platform/ext/common/tfm_hal_spm_logdev.h
@@ -19,6 +19,6 @@
  * \retval >=0           Number of chars output.
  * \retval <0            TFM HAL error code.
  */
-int32_t tfm_hal_output_spm_log(const unsigned char *str, uint32_t len);
+int32_t tfm_hal_output_spm_log(const char *str, uint32_t len);
 
 #endif /* __TFM_HAL_SPM_LOGDEV_H__ */
diff --git a/secure_fw/spm/include/tfm_spm_log.h b/secure_fw/spm/include/tfm_spm_log.h
index 611fc23..3a00838 100644
--- a/secure_fw/spm/include/tfm_spm_log.h
+++ b/secure_fw/spm/include/tfm_spm_log.h
@@ -60,6 +60,6 @@
  * \retval >=0        Number of chars output.
  * \retval <0         TFM HAL error code.
  */
-int32_t spm_log_msgval(const unsigned char *msg, size_t len, uint32_t value);
+int32_t spm_log_msgval(const char *msg, size_t len, uint32_t value);
 
 #endif /* __TFM_SPM_LOG_H__ */