xen: x86: remove setting the obsolete config XEN_MAX_DOMAIN_MEMORY

xen: x86: remove setting the obsolete config XEN_MAX_DOMAIN_MEMORY

Commit c70727a5bc18 ("xen: allow more than 512 GB of RAM for 64 bit
pv-domains") from July 2015 replaces the config XEN_MAX_DOMAIN_MEMORY with
a new config XEN_512GB, but misses to adjust arch/x86/configs/xen.config.
As XEN_512GB defaults to yes, there is no need to explicitly set any config
in xen.config.

Just remove setting the obsolete config XEN_MAX_DOMAIN_MEMORY.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20220817044333.22310-1-lukas.bulwahn@gmail.com
Signed-off-by: Juergen Gross <jgross@suse.com>