BCVs should inherrit the legacy harddrive priority.

A BCV will (almost assuredly) be a hard drive, so it makes sense to
prioritize them the same as builtin hard drives when only the legacy
priority system is used.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
diff --git a/src/boot.c b/src/boot.c
index 93928d3..e26dad1 100644
--- a/src/boot.c
+++ b/src/boot.c
@@ -326,7 +326,7 @@
 boot_add_bcv(u16 seg, u16 ip, u16 desc, int prio)
-    bootentry_add(IPL_TYPE_BCV, defPrio(prio, DEFAULT_PRIO)
+    bootentry_add(IPL_TYPE_BCV, defPrio(prio, DefaultHDPrio)
                   , SEGOFF(seg, ip).segoff
                   , desc ? MAKE_FLATPTR(seg, desc) : "Legacy option rom");