Leave the OCOTP turned on, so that we subsequent access do not fail.

After enabling the thermal driver on a mx6sxsabresd board:

U-Boot 2015.01-rc1-18267-g99d4189-dirty (Nov 24 2014 - 12:59:01)

CPU:   Freescale i.MX6SX rev1.0 at 792 MHz
CPU:   Temperature 48 C
Reset cause: POR
Board: MX6SX SABRE SDB
I2C:   ready
DRAM:  1 GiB
PMIC:  PFUZE100 ID=0x10
MMC:   FSL_SDHC: 0, FSL_SDHC: 1, FSL_SDHC: 2
  00:01.0     - 16c3:abcd - Bridge device
   01:00.0    - 8086:08b1 - Network controller
In:    serial
Out:   serial
Err:   serial
Net:
(hang)

As the thermal driver accesses the ocotp registers, its clock will be disabled
afterwards.

Then when the MAC address is read (also from ocotp registers) it will cause a
hang.

Do not disable the ocotp clock to prevent this problem.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Reviewed-by: Benoît Thébaudeau <benoit.thebaudeau.dev@gmail.com>