pata_platform: Document `pio_mask' module parameter

Add MODULE_PARM_DESC documentation and a kernel-parameters.txt entry.

Signed-off-by: Maciej W. Rozycki <[e-mail]>
Reviewed-by: Christoph Hellwig <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jens Axboe <[e-mail]>

Documentation/admin-guide/kernel-parameters.txt

···
 			By default set to 1 if CONFIG_PATA_WINBOND_VLB_MODULE,
 			0 otherwise.
 
+	pata_platform.pio_mask=	[HW,LIBATA]
+			Format: <int>
+			Supported PIO mode mask.  Set individual bits to allow
+			the use of the respective PIO modes.  Bit 0 is for
+			mode 0, bit 1 is for mode 1, and so on.  Mode 0 only
+			allowed by default.
+
 	pause_on_oops=
 			Halt all CPUs after the first oops has been printed for
 			the specified number of seconds.  This is to be used if

drivers/ata/pata_platform.c

···
 #define DRV_VERSION "1.2"
 
 static int pio_mask = 1;
+module_param(pio_mask, int, 0);
+MODULE_PARM_DESC(pio_mask, "PIO modes supported, mode 0 only by default");
 
 /*
  * Provide our own set_mode() as we don't want to change anything that has
···
 };
 
 module_platform_driver(pata_platform_driver);
-
-module_param(pio_mask, int, 0);
 
 MODULE_AUTHOR("Paul Mundt");
 MODULE_DESCRIPTION("low-level driver for platform device ATA");