mtd: devices: powernv_flash: Add function names to headers and fix 'dev'

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

 drivers/mtd/devices/powernv_flash.c:129: warning: Cannot understand  * @mtd: the device
 drivers/mtd/devices/powernv_flash.c:145: warning: Cannot understand  * @mtd: the device
 drivers/mtd/devices/powernv_flash.c:161: warning: Cannot understand  * @mtd: the device
 drivers/mtd/devices/powernv_flash.c:184: warning: Function parameter or member 'dev' not described in 'powernv_flash_set_driver_info'

Cc: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Vignesh Raghavendra <vigneshr@ti.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: linux-mtd@lists.infradead.org
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20201109182206.3037326-24-lee.jones@linaro.org

drivers/mtd/devices/powernv_flash.c

@@ -126,6 +126,7 @@ static int powernv_flash_async_op(struct mtd_info *mtd, enum flash_op op,
 }
 
 /**
+ * powernv_flash_read
  * @mtd: the device
  * @from: the offset to read from
  * @len: the number of bytes to read
@@ -142,6 +143,7 @@ static int powernv_flash_read(struct mtd_info *mtd, loff_t from, size_t len,
 }
 
 /**
+ * powernv_flash_write
  * @mtd: the device
  * @to: the offset to write to
  * @len: the number of bytes to write
@@ -158,6 +160,7 @@ static int powernv_flash_write(struct mtd_info *mtd, loff_t to, size_t len,
 }
 
 /**
+ * powernv_flash_erase
  * @mtd: the device
  * @erase: the erase info
  * Returns 0 if erase successful or -ERRNO if an error occurred
@@ -176,7 +179,7 @@ static int powernv_flash_erase(struct mtd_info *mtd, struct erase_info *erase)
 
 /**
  * powernv_flash_set_driver_info - Fill the mtd_info structure and docg3
- * structure @pdev: The platform device
+ * @dev: The device structure
  * @mtd: The structure to fill
  */
 static int powernv_flash_set_driver_info(struct device *dev,