ANDROID: dm kcopyd: Use reserved memory for the copy buffer

MediaTek needs to use specific reserved memory for merge buffer
to ensure the data correctness during merge period.

The specific path would be enabled only if bootarg "mtk_kcopyd_quirk"
is well defined to be isolated for MediaTek platform only.

The format of bootarg would be: mtk_kcopyd_quirk=mediatek,dm_ota
where "dm_ota" is exact the name of the reserved memory.

Bug: 223346425
Change-Id: I2b295ca8c0cea65146077324c58ac17c05fe0099
Signed-off-by: Will Shiu <Will.Shiu@mediatek.com>
Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Akilesh Kailash <akailash@google.com>