[SCSI] qla2xxx: Correct Atmel flash-part handling.

Use correct block size (4K) for erase command 0x20 for Atmel
Flash. Use dword addresses for determining sector boundary.

Cc: Stable Tree <stable@kernel.org>
Signed-off-by: Lalit Chandivade <lalit.chandivade@qlogic.com>
Signed-off-by: Andrew Vasquez <andrew.vasquez@qlogic.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>