mtd: dataflash: Improve coding style in jedec_probe()

Change the following:

   - Replace indentation between type and name of local variable from
     tabs to spaces

   - Replace magic number 0x1F with CFI_MFR_ATMEL macro

   - Replace variable 'tmp' with 'ret' and 'i' where appropriate

   - Reformat multi-line comments and add newlines where appropriate

No functional change intended.

Cc: cphealy@gmail.com
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Brian Norris <computersforpeace@gmail.com>
Cc: Boris Brezillon <boris.brezillon@free-electrons.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Cyrille Pitchen <cyrille.pitchen@atmel.com>
Cc: Marek Vasut <marek.vasut@gmail.com>
Cc: linux-kernel@vger.kernel.org
Acked-by: Marek Vasut <marek.vasut@gmail.com>
Tested-by: Chris Healy <cphealy@gmail.com>
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>