nand read.jffs2 (nand_legacy) in common/cmd_nand.c

Error with CONFIG_NAND_LEGACY in common/cmd_nand.c:
With current code "nand read.jffs2s" (read and skip bad blocks) is always interpreted as
"nand read.jffs2" (read and fill bad blocks with 0xff). This is because ".jffs2" is
tested before ".jffs2s" and only the first two characters are compared.

Correction:
Test for ".jffs2s" first and compare the first 7 characters.

Signed-off-by: Scott Wood <scottwood@freescale.com>