Break down BL1 AArch64 synchronous exception handler
Break down BL1 AArch64 synchronous exception handler

The AArch64 synchronous exception vector code in BL1 is almost
reaching its architectural limit of 32 instructions. This means
there is very little space for this code to grow.

This patch reduces the size of the exception vector code by
moving most of its code in a function to which we branch from
SynchronousExceptionA64.

Change-Id: Ib35351767a685fb2c2398029d32e54026194f7ed

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