qemu-options.hx: Document -M as -machine alias

-M is used heavily in documentation and scripts, but isn't actually
documented anywhere.

Document it as equivalent to -machine, also moving to -machine the sole
suboption that was documented under -M.

Reported-by: Julian Andres Klode <jak@jak-linux.org>
Signed-off-by: Dr. David Alan Gilbert <dave@treblig.org>
Link: https://lore.kernel.org/r/20251203131511.153460-1-dave@treblig.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

qemu-options.hx

@@ -44,6 +44,7 @@ DEF("machine", HAS_ARG, QEMU_OPTION_machine, \
 #endif
     "                memory-backend='backend-id' specifies explicitly provided backend for main RAM (default=none)\n"
     "                cxl-fmw.0.targets.0=firsttarget,cxl-fmw.0.targets.1=secondtarget,cxl-fmw.0.size=size[,cxl-fmw.0.interleave-granularity=granularity]\n"
+    "                sgx-epc.0.memdev=memid,sgx-epc.0.node=numaid\n"
     "                smp-cache.0.cache=cachename,smp-cache.0.topology=topologylevel\n",
     QEMU_ARCH_ALL)
 SRST
@@ -179,6 +180,9 @@ SRST
 
             -machine cxl-fmw.0.targets.0=cxl.0,cxl-fmw.0.targets.1=cxl.1,cxl-fmw.0.size=128G,cxl-fmw.0.interleave-granularity=512
 
+    ``sgx-epc.0.memdev=@var{memid},sgx-epc.0.node=@var{numaid}``
+        Define an SGX EPC section.
+
     ``smp-cache.0.cache=cachename,smp-cache.0.topology=topologylevel``
         Define cache properties for SMP system.
 
@@ -208,12 +212,10 @@ SRST
 ERST
 
 DEF("M", HAS_ARG, QEMU_OPTION_M,
-    "                sgx-epc.0.memdev=memid,sgx-epc.0.node=numaid\n",
-    QEMU_ARCH_ALL)
-
+    "-M              as -machine\n", QEMU_ARCH_ALL)
 SRST
-``sgx-epc.0.memdev=@var{memid},sgx-epc.0.node=@var{numaid}``
-    Define an SGX EPC section.
+``-M``
+    as -machine.
 ERST
 
 DEF("cpu", HAS_ARG, QEMU_OPTION_cpu,