main/msm-firmware-loader: fix shellcheck failure (MR 2752)

A recent(?) update in shellcheck made this fail, possibly because the
test in shellcheck was fixed(?) or ???

The failure this fixes is:

Test with shellcheck: ./main/msm-firmware-loader/msm-firmware-loader.sh
In msm-firmware-loader.sh line 49:
	if [ -z "${FW_PARTITIONS##*$PARTNAME*}" ] && [ -n "$PARTNAME" ]
                                   ^-------^ SC2295 (info): Expansions inside ${..} need to be quoted separately, otherwise they match as patterns.

[ci:skip-build] already built successfully in CI

main/msm-firmware-loader/APKBUILD

 pkgname=msm-firmware-loader
 pkgver=1
-pkgrel=1
+pkgrel=2
 pkgdesc="Set of init services to automatically load firmware from device partitions"
 url="https://postmarketos.org/"
 subpackages="$pkgname-wcnss"
@@ -42,7 +42,7 @@ wcnss() {
 }
 
 sha512sums="
-ce6d8a072673bcdf6a3b24455d690291c87046802a460742271c2465db3326a09792b7c0c3e07d3e741b75cc34a5e416a64899153a0b920149e70718d0188761  msm-firmware-loader.sh
+e311f589c55670974f300f821a49baf54f4966ab5617dbaeef43389be013f1139490b8cfdc7ef4e3c59b6f0013ea1b2c50b37487c6d22104f8dc6d287c158fac  msm-firmware-loader.sh
 d9ad3b21564de9a4970a8923b8598fb46a54543ac9f1494676a6833800bc68c64f230737b308fec54aae09c2cf635794e8f1abc46253b0386260b4580587483d  msm-firmware-loader.initd
 93063f24b64206f4e6115ca0276d47bb65e1c510fc56fe1a939030d09d3b63cf07f001fb789309bb317f787cbe687906258bb5eb961a9ea90568f672378e86ea  msm-firmware-loader-unpack.sh
 616a28c3a65a45bb65f798989d93daacdeea08a90a9a8538b5bac2d73b2c8b135554ecaf49b4084829f88af760a144802adcd89b50f46bc267d6b04c9c733ff8  msm-firmware-loader-unpack.initd

main/msm-firmware-loader/msm-firmware-loader.sh

@@ -46,7 +46,7 @@ do
 	DEVNAME="$(grep DEVNAME "$part"/uevent | sed 's/DEVNAME=//g')"
 	PARTNAME="$(grep PARTNAME "$part"/uevent | sed 's/PARTNAME=//g')"
 
-	if [ -z "${FW_PARTITIONS##*$PARTNAME*}" ] && [ -n "$PARTNAME" ]
+	if [ -z "${FW_PARTITIONS##*"$PARTNAME"*}" ] && [ -n "$PARTNAME" ]
 	then
 		mkdir "$BASEDIR/mnt/$PARTNAME"
 		mount -o ro,nodev,noexec,nosuid \