mtd: spi-nor: fix kernel-doc for spi_nor::spimem

When adding the 'spimem' field to 'struct spi_nor', a grammar mistake
("point" instead of "pointer") was made -- fix it and convert the SPI
acronym to uppercase and fully spell out "memory", while at it...

Fixes: b35b9a10 ("mtd: spi-nor: Move m25p80 code in spi-nor.c")
Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>

include/linux/mtd/spi-nor.h

@@ -331,7 +331,7 @@ struct spi_nor_flash_parameter;
  * @mtd:		an mtd_info structure
  * @lock:		the lock for the read/write/erase/lock/unlock operations
  * @dev:		pointer to an SPI device or an SPI NOR controller device
- * @spimem:		point to the spi mem device
+ * @spimem:		pointer to the SPI memory device
  * @bouncebuf:		bounce buffer used when the buffer passed by the MTD
  *                      layer is not DMA-able
  * @bouncebuf_size:	size of the bounce buffer