sandbox: scsi: Move block size into shared struct

Move this information into struct scsi_emul_info so we can use it in
common code.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/scsi_emul.h b/include/scsi_emul.h
index b281c16..86c9379 100644
--- a/include/scsi_emul.h
+++ b/include/scsi_emul.h
@@ -17,6 +17,7 @@
  *
  * @vendor: Vendor name
  * @product: Product name
+ * @block_size: Block size of device in bytes (normally 512)
  *
  * @phase: Current SCSI phase
  * @buff_used: Number of bytes ready to transfer back to host
@@ -30,6 +31,7 @@
 	void *buff;
 	const char *vendor;
 	const char *product;
+	int block_size;
 
 	/* state maintained by the emulator: */
 	enum scsi_cmd_phase phase;