mtd: spear_smi: fix kernel-doc warnings <linux/mtd/spear_smi.h>

mtd: spear_smi: fix kernel-doc warnings <linux/mtd/spear_smi.h>

Correct most kernel-doc warnings in include/linux/mtd/spear_smi.h
by adding a leading '@' to the description of struct members.
Add a new description for the missing @np member.

Warning: spear_smi.h:48 struct member 'name' not described
 in 'spear_smi_flash_info'
Warning: spear_smi.h:48 struct member 'mem_base' not described
 in 'spear_smi_flash_info'
Warning: spear_smi.h:48 struct member 'size' not described
 in 'spear_smi_flash_info'
Warning: spear_smi.h:48 struct member 'partitions' not described
 in 'spear_smi_flash_info'
Warning: spear_smi.h:48 struct member 'nr_partitions' not described
 in 'spear_smi_flash_info'
Warning: spear_smi.h:48 struct member 'fast_mode' not described
 in 'spear_smi_flash_info'
Warning: spear_smi.h:62 struct member 'clk_rate' not described
 in 'spear_smi_plat_data'
Warning: spear_smi.h:62 struct member 'num_flashes' not described
 in 'spear_smi_plat_data'
Warning: spear_smi.h:62 struct member 'board_flash_info' not described
 in 'spear_smi_plat_data'
Warning: spear_smi.h:62 struct member 'np' not described
 in 'spear_smi_plat_data'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>