[MTD] rtc_from4 error status check, disable virtual erase blocks

Added routine to perform extra error status checks on erase and write
failures to determine if errors are correctable.
Added option to prevent JFFS2 from using virtual erase blocks.
Performed minor cleanup on whitespace and comments.

Signed-off-by: David A. Marlin <dmarlin@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>