mfd: cros_ec: Fix and improve kerneldoc comments.

cros-ec includes inside the MFD subsystem, specially the file
cros_ec_commands.h, has been modified several times and it has grown a
lot, unfortunately, we didn't have care too much about the documentation.
This patch tries to improve the documentation and also fixes all the
issues reported by kerneldoc script.
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: Benson Leung <bleung@chromium.org>

drivers/mfd/cros_ec_dev.h

@@ -26,12 +26,13 @@
 
 #define CROS_EC_DEV_VERSION "1.0.0"
 
-/*
- * @offset: within EC_LPC_ADDR_MEMMAP region
- * @bytes: number of bytes to read. zero means "read a string" (including '\0')
- *         (at most only EC_MEMMAP_SIZE bytes can be read)
- * @buffer: where to store the result
- * ioctl returns the number of bytes read, negative on error
+/**
+ * struct cros_ec_readmem - Struct used to read mapped memory.
+ * @offset: Within EC_LPC_ADDR_MEMMAP region.
+ * @bytes: Number of bytes to read. Zero means "read a string" (including '\0')
+ *         At most only EC_MEMMAP_SIZE bytes can be read.
+ * @buffer: Where to store the result. The ioctl returns the number of bytes
+ *         read or negative on error.
  */
 struct cros_ec_readmem {
 	uint32_t offset;