DMAResource: Validate that alignment <= block_size.

The code here cannot handle the case where alignment > block_size,
so anything calling Init() with these parameters is invalid.

Fixes #15902 (nvme_disk was long since adjusted, so this is a defense
against code being written in the future.)

src/system/kernel/device_manager/dma_resources.cpp

@@ -158,6 +158,8 @@ status_t
 DMAResource::Init(const dma_restrictions& restrictions,
 	generic_size_t blockSize, uint32 bufferCount, uint32 bounceBufferCount)
 {
+	ASSERT(restrictions.alignment <= blockSize);
+
 	fRestrictions = restrictions;
 	fBlockSize = blockSize == 0 ? 1 : blockSize;
 	fBufferCount = bufferCount;