kernel: add missing config option

CONFIG_NVMEM_BCM_OCOTP was added in kernel 4.10 and it is possible to
activate it on the bcm53xx target. Deactivate it by default to fix the
build of the bcm53xx target.
This was found by build bot.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

target/linux/generic/config-4.14

@@ -3283,6 +3283,7 @@ CONFIG_NMI_LOG_BUF_SHIFT=13
 # CONFIG_NTP_PPS is not set
 # CONFIG_NVM is not set
 # CONFIG_NVMEM is not set
+# CONFIG_NVMEM_BCM_OCOTP is not set
 # CONFIG_NVMEM_IMX_OCOTP is not set
 # CONFIG_NVME_FC is not set
 # CONFIG_NVME_TARGET is not set