arm64/sysreg: Fix typo in Enum element regex

arm64/sysreg: Fix typo in Enum element regex

In the awk script, there was a typo with the comparison operator when
checking if the matched pattern is inside an Enum block.
This prevented the generation of the whole sysreg-defs.h header.

Fixes: 66847e0618d7 ("arm64: Add sysreg header generation scripting")
Signed-off-by: Alejandro Tafalla <atafalla@dnyon.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220609204220.12112-1-atafalla@dnyon.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>