nvmem: Fix misspelling

There is no function called kstrbool().

Signed-off-by: Matthew Wilcox (Oracle) <[e-mail]>
Reviewed-by: Marek Vasut <[e-mail]>
Signed-off-by: Srinivas Kandagatla <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/ABI/stable/sysfs-bus-nvmem

···
 		Read returns '0' or '1' for read-write or read-only modes
 		respectively.
 		Write parses one of 'YyTt1NnFf0', or [oO][NnFf] for "on"
-		and "off", i.e. what kstrbool() supports.
+		and "off", i.e. what kstrtobool() supports.
 		Note: This file is only present if CONFIG_NVMEM_SYSFS
 		is enabled.