imx: nandbcb: Fix resource leak in read_fcb

Fix Coverity Issue 9006657. In read_fcb, leak of memory to system
resource "fcb_raw_page". Adjust the sequence to check the mtd bad
block prior than allocation of "fcb_raw_page", also check the NULL
return of allocation.

Signed-off-by: Ye Li <ye.li@nxp.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
1 file changed