CFI: fix warning: variable ... set but not used

Fix:
cfi_mtd.c: In function 'cfi_mtd_init':
cfi_mtd.c:226:19: warning: variable 'mtd_list' set but not used [-Wunused-but-set-variable]
cfi_mtd.c: In function 'cfi_mtd_init':
cfi_mtd.c:225:6: warning: unused variable 'devices_found'
cfi_mtd.c: In function 'cfi_mtd_init':
cfi_mtd.c:226:19: warning: variable 'mtd_list' set but not used [-Wunused-but-set-variable]
[-Wunused-variable]

Signed-off-by: Wolfgang Denk <wd@denx.de>
Cc: Stefan Roese <sr@denx.de>
Acked-by: Stefan Roese <sr@denx.de>