shell cmd msdosfmt a NOOP (in 4.9.1) for SD/MMC

[Gene Smith]

I tried the shell command msdosfmt again on my MMC and still nothing 
happens. I thought I had all my drivers working OK. It gets to the point 
in the format code where it wants to write a block to flash but the 
"write_entry" for the driver is NULL so nothing happens. However, no 
error is flagged so the shell still prints "formatting successful."

The write_entry is the NULL entry for sd_card_disk_ops in spi-sd-card.c. 
When I change it from NULL and set it to sd_card_driver_write (a 
function in the same file that I had never seen called) msdosfmt 
attempts to do the write of the block with this function.

However, it still fails inside sd_card_driver_write(). I think because 
the driver table "e" that it gets with the call to 
sd_card_driver_get_entry() is bad since the "major number" is 8 (a 2nd 
instance) instead of "major number" 9 (the first instance with the flash 
info set correctly). This kludge fixes it inside 4.9.1's 
sd_card_driver_write():

	/* Get driver entry */
#if 0
	rv = sd_card_driver_get_entry(minor, &e);
	CHECK_RVSC( rv, "Get driver entry");
#else
	e = &sd_card_driver_table[0];
#endif

	/* Start */
	sc = sd_card_start(e);   <---this failed with #if 0 code!

I made the same change in sd_card_driver_read(), not sure if it is called.

Looking at the HEAD version of spi-sd-card.c, I see it has been changed 
so that there would only be a single "major" instance generated per bus 
device (in my case one SPI device).  Also functions 
sd_card_driver_write/read() are removed from HEAD. However, the 
"write_entry" function is now rtems_blkdev_generic_write (not defined in 
4.9.1). Hopefully the correct function will be called when msdosfmt code 
calls rtems_blkdev_generic_write().

-gene