libdrgn: fix typo in ORC unwinder handling of ORC_REG_SP_INDIRECT

ORC_REG_SP_INDIRECT is supposed to be an indirect access via rsp, but we
have a typo and are using rbp instead. This is a partial fix for #304.

Fixes: 630d39e ("libdrgn: add ORC unwinder")
Signed-off-by: Omar Sandoval <[email protected]>

Author: osandov

libdrgn/arch_x86_64.c

@@ -76,7 +76,7 @@ orc_to_cfi_x86_64(const struct drgn_orc_entry *orc,
 		break;
 	case ORC_REG_SP_INDIRECT:
 		rule.kind = DRGN_CFI_RULE_AT_REGISTER_ADD_OFFSET;
-		rule.regno = DRGN_REGISTER_NUMBER(rbp);
+		rule.regno = DRGN_REGISTER_NUMBER(rsp);
 		rule.offset = orc->sp_offset;
 		break;
 	case ORC_REG_BP_INDIRECT: