target/xtensa: add file-IO support

- Manual integration of File-IO support from xt0.2 release
- Verified with applications linked using gdbio LSP
- No new clang static analysis warnings

Signed-off-by: Ian Thompson <ianst@cadence.com>
Change-Id: Iedc5f885b2548097ef4f11ae1a675b5944f5fdf0
Reviewed-on: https://review.openocd.org/c/openocd/+/7550
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

src/target/xtensa/xtensa.c

@@ -1544,6 +1544,7 @@ int xtensa_prepare_resume(struct target *target,
 		LOG_TARGET_WARNING(target, "target not halted");
 		return ERROR_TARGET_NOT_HALTED;
 	}
+	xtensa->halt_request = false;
 
 	if (address && !current) {
 		xtensa_reg_set(target, XT_REG_IDX_PC, address);