qapi/misc-target: Fix the doc to distinguish query-sgx and query-sgx-capabilities

qapi/misc-target: Fix the doc to distinguish query-sgx and query-sgx-capabilities

There're 2 QMP commands: query-sgx and query-sgx-capabilities, but
their outputs are very similar and the documentation lacks clear
differentiation.

From the codes, query-sgx is used to gather guest's SGX capabilities
(including SGX related CPUIDs and EPC sections' size, in SGXInfo), and
if guest doesn't have SGX, then QEMU will report the error message.

On the other hand, query-sgx-capabilities is used to gather host's SGX
capabilities (descripted by SGXInfo as well). And if host doesn't
support SGX, then QEMU will also report the error message.

Considering that SGXInfo is already documented and both these 2 commands
have enough error messages (for the exception case in their codes).

Therefore the QAPI documentation for these two commands only needs to
emphasize that one of them applies to the guest and the other to the
host.

Fix their documentation to reflect this difference.

Reported-by: Markus Armbruster <armbru@redhat.com>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Link: https://lore.kernel.org/r/20250513143131.2008078-3-zhao1.liu@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>