The CCM code as originally written attempted to use as few NEON
registers as possible, to avoid having to eagerly preserve/restore the
entire NEON register file at every call to kernel_neon_begin/end. At
that time, this API took a number of NEON registers as a parameter, and
only preserved that many registers.

Today, the NEON register file is restored lazily, and the old API is
long gone. This means we can use as many NEON registers as we can make
meaningful use of, which means in the AES case that we can keep all
round keys in registers rather than reloading each of them for each AES
block processed.

On Cortex-A53, this results in a speedup of more than 50%. (From 4
cycles per byte to 2.6 cycles per byte)
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>