selftests: kvm: s390: Add kvm_s390_sie_block definition for userspace tests

selftests: kvm: s390: Add kvm_s390_sie_block definition for userspace tests

Subsequent tests do require direct manipulation of the SIE control
block. This commit introduces the SIE control block definition for use
within the selftests.

There are already definitions of this within the kernel.
This differs in two ways.
* This is the first definition of this in userspace.
* In the context of the selftests this does not require atomicity for
  the flags.

With the userspace definition of the SIE block layout now being present
we can reuse the values in other tests where applicable.

Signed-off-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Link: https://lore.kernel.org/r/20240807154512.316936-3-schlameuss@linux.ibm.com
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Message-ID: <20240807154512.316936-3-schlameuss@linux.ibm.com>