bus: fsl-mc: mc-sys: Supply missing function names in kernel-doc headers

Fixes the following W=1 kernel build warning(s):

drivers/bus/fsl-mc/mc-sys.c:20: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
drivers/bus/fsl-mc/mc-sys.c:151: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
drivers/bus/fsl-mc/mc-sys.c:197: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
drivers/bus/fsl-mc/mc-sys.c:237: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst

Cc: Stuart Yoder <[e-mail]>
Reviewed-by: Laurentiu Tudor <[e-mail]>
Signed-off-by: Lee Jones <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/bus/fsl-mc/mc-sys.c

···
 
 #include "fsl-mc-private.h"
 
-/**
+/*
  * Timeout in milliseconds to wait for the completion of an MC command
  */
 #define MC_CMD_COMPLETION_TIMEOUT_MS	500
···
 }
 
 /**
- * Waits for the completion of an MC command doing preemptible polling.
- * uslepp_range() is called between polling iterations.
- *
+ * mc_polling_wait_preemptible() - Waits for the completion of an MC
+ *                                 command doing preemptible polling.
+ *                                 uslepp_range() is called between
+ *                                 polling iterations.
  * @mc_io: MC I/O object to be used
  * @cmd: command buffer to receive MC response
  * @mc_status: MC command completion status
···
 }
 
 /**
- * Waits for the completion of an MC command doing atomic polling.
- * udelay() is called between polling iterations.
- *
+ * mc_polling_wait_atomic() - Waits for the completion of an MC command
+ *                            doing atomic polling. udelay() is called
+ *                            between polling iterations.
  * @mc_io: MC I/O object to be used
  * @cmd: command buffer to receive MC response
  * @mc_status: MC command completion status
···
 }
 
 /**
- * Sends a command to the MC device using the given MC I/O object
- *
+ * mc_send_command() - Sends a command to the MC device using the given
+ *                     MC I/O object
  * @mc_io: MC I/O object to be used
  * @cmd: command to be sent
  *