meta-ampere: fix shellcheck issues

Fix all issues from the shellcheck checked on bash shells under
meta-ampere.

Tested: Verify the following features:
1. Power control (on,off, cycle, graceful shutdown, hard reset).
2. UART switching.
3. UEFI firmware update.

Signed-off-by: Thang Q. Nguyen <thang@os.amperecomputing.com>
Change-Id: Idabf839b7521ecadb642230cc8bb3472c787002e
diff --git a/meta-ampere/meta-jade/recipes-ampere/platform/mtjade-utils/gpio-defs.sh b/meta-ampere/meta-jade/recipes-ampere/platform/mtjade-utils/gpio-defs.sh
index 7c887d4..fc0edd6 100644
--- a/meta-ampere/meta-jade/recipes-ampere/platform/mtjade-utils/gpio-defs.sh
+++ b/meta-ampere/meta-jade/recipes-ampere/platform/mtjade-utils/gpio-defs.sh
@@ -1,3 +1,6 @@
+#!/bin/sh
+
+# shellcheck disable=SC2034
 # Index of GPIO device in gpioget/gpioset
 GPIO_CHIP0_IDX=0
 GPIO_CHIP1_IDX=1