target/arm: Add dummy needed functions to M profile vmstate subsections

Currently the migration code incorrectly treats a subsection with
no .needed function pointer as if it was the subsection list
terminator -- it is ignored and so is everything after it.
Work around this by giving various M profile vmstate structs
a 'needed' function that always returns true.
We reuse m_needed() for this, since it's always true here.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: NRichard Henderson <richard.henderson@linaro.org>
Message-id: 20180806123445.1459-4-peter.maydell@linaro.org

target/arm/machine.c

@@ -184,6 +184,7 @@ static const VMStateDescription vmstate_m_faultmask_primask = {
     .name = "cpu/m/faultmask-primask",
     .version_id = 1,
     .minimum_version_id = 1,
+    .needed = m_needed,
     .fields = (VMStateField[]) {
         VMSTATE_UINT32(env.v7m.faultmask[M_REG_NS], ARMCPU),
         VMSTATE_UINT32(env.v7m.primask[M_REG_NS], ARMCPU),
@@ -230,6 +231,7 @@ static const VMStateDescription vmstate_m_scr = {
     .name = "cpu/m/scr",
     .version_id = 1,
     .minimum_version_id = 1,
+    .needed = m_needed,
     .fields = (VMStateField[]) {
         VMSTATE_UINT32(env.v7m.scr[M_REG_NS], ARMCPU),
         VMSTATE_END_OF_LIST()
@@ -240,6 +242,7 @@ static const VMStateDescription vmstate_m_other_sp = {
     .name = "cpu/m/other-sp",
     .version_id = 1,
     .minimum_version_id = 1,
+    .needed = m_needed,
     .fields = (VMStateField[]) {
         VMSTATE_UINT32(env.v7m.other_sp, ARMCPU),
         VMSTATE_END_OF_LIST()