arm64/fp: Rename SVE and SME LEN field name to _WIDTH

The SVE and SVE length configuration field LEN have constants specifying
their width called _SIZE rather than the more normal _WIDTH, in preparation
for automatic generation rename to _WIDTH. No functional change.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220510161208.631259-3-broonie@kernel.org


Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>