Fix incorrect assertions in bl1_main()
Fix incorrect assertions in bl1_main()

The validation of the caching enable state in bl1_main() was
incorrect resulting in the state not being checked. Using the right
operator fixes this.

Change-Id: I2a99478f420281a1dcdf365d3d4fd8394cd21b51

jcastillo-arm/arm-trusted-firmware,idl3r/arm-trusted-firmware,lsigithub/arm-trusted-firmware_public,sbranden/arm-trusted-firmware,sandrine-bailleux/arm-trusted-firmware,davwan01/arm-trusted-firmware,sandrine-bailleux-arm/arm-trusted-firmware,robixnai/arm-trusted-firmware,mtk09422/arm-trusted-firmware,jcastillo-arm/arm-trusted-firmware,idl3r/arm-trusted-firmware,achingupta/arm-trusted-firmware,davwan01/arm-trusted-firmware,lsigithub/arm-trusted-firmware_public,sandrine-bailleux-arm/arm-trusted-firmware,sandrine-bailleux/arm-trusted-firmware,achingupta/arm-trusted-firmware,robixnai/arm-trusted-firmware,mtk09422/arm-trusted-firmware,sbranden/arm-trusted-firmware