[MTD] mtdchar.c remove shadowed variable warnings

Use einfo, oinfo for the inner erase_info and otp_info structs used in
individual case statements.

drivers/mtd/mtdchar.c:582:26: warning: symbol 'info' shadows an earlier one
drivers/mtd/mtdchar.c:380:23: originally declared here
drivers/mtd/mtdchar.c:596:26: warning: symbol 'info' shadows an earlier one
drivers/mtd/mtdchar.c:380:23: originally declared here
drivers/mtd/mtdchar.c:704:19: warning: symbol 'info' shadows an earlier one
drivers/mtd/mtdchar.c:380:23: originally declared here

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>