MAINTAINERS: Add Dave Hansen as reviewer for INTEL SGX

Add Dave as reviewer for INTEL SGX patches.

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lkml.kernel.org/r/20210205151546.144810-1-jarkko@kernel.org