arm64: sysreg: Drag linux/kconfig.h to work around vdso build issue

Broonie reports that fed55f4 ("arm64: errata: Work around
AmpereOne's erratum AC04_CPU_23") breaks one of the vdso selftests
(vdso_test_chacha) as it indirectly drags asm/sysreg.h.

It is rather unfortunate (and worrying) that userspace gets built
with non-UAPI headers. In any case, paper over the issue by dragging
linux/kconfig.h in asm/sysreg.h. It is the right thing to do, at
least from the kernel perspective.

Reported-by: Mark Brown <broonie@kernel.org>
Fixes: fed55f4 ("arm64: errata: Work around AmpereOne's erratum AC04_CPU_23")
Link: https://lore.kernel.org/r/aDCDGZ-G-nCP3hJI@finisterre.sirena.org.uk
Cc: D Scott Phillips <scott@os.amperecomputing.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Oliver Upton <oliver.upton@linux.dev>
Cc: Will Deacon <will@kernel.org>
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20250523170208.530818-1-maz@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>

Author: Marc Zyngier

arch/arm64/include/asm/sysreg.h

@@ -12,6 +12,7 @@
 #include <linux/bits.h>
 #include <linux/stringify.h>
 #include <linux/kasan-tags.h>
+#include <linux/kconfig.h>
 
 #include <asm/gpr-num.h>