device-samsung-manta: make wifi-macaddr.sh pass shellcheck (MR 4783)

Signed-off-by: Alexandre Marquet <tb@a-marquet.fr>

device/testing/device-samsung-manta/APKBUILD

@@ -3,7 +3,7 @@
 # Co-Maintainer: Alexandre Marquet <tb@a-marquet.fr>
 pkgname=device-samsung-manta
 pkgdesc="Google Nexus 10"
-pkgver=5
+pkgver=6
 pkgrel=0
 url="https://postmarketos.org"
 license="MIT"
@@ -60,6 +60,6 @@ sha512sums="
 2816b1389f46255a2ece6fca9dff776ad0f6a8a7d642954da9277c9af3ae383d19866370a8fba24cf1d57eb4305e956df246ffd4ee8f45032962f478d66c2c68  deviceinfo
 e00c58936fa4340f8531538136ad028d002342a4399b68d26190b931831108007486257f9d8a48c3ed454696b45d176b1497d624c33ace21e61eba33ac7ce136  modules-initfs
 37a18d36e1e08ddcc605de73214dc02a9e7737f6a66b2e4be301fca816bbf3c2ba6b5ead1f12c745fd0fa019e2a8e959e4fc20386ad94ca7277d4c7d7f9fb703  100-wlan-mac.rules
-ef18bd3e5c4c8c69dce3293c9e70fa0b30820ba12cb8217346b63392db95513169c31e9bf730aac5cecea15e2cda4166b093bbf0e456055a5432e57400ecb9b1  wifi-macaddr.sh
+cfba48f87335ed8810004e02db165203149532ade7be206947f8195bbcc14d61bf3a898378566aca7295ba08784665f462442bf5e74d7f58b2cc62d996376317  wifi-macaddr.sh
 5c3a692f22a29fca792c114c6d94ff1bf0d6921f068f207a2894a8f99c73dcc319e7c803ed7adfe64eb3e60088f37e2a2730118b2ed57aa01b35415664085567  networkmanager.conf
 "

device/testing/device-samsung-manta/wifi-macaddr.sh

 #!/bin/sh
 
-macaddr=$(cat /proc/cmdline | sed -n "s/^.*androidboot\.wifimacaddr=\(\([0-9A-Fa-f]\{2\}:\)\{5\}[0-9A-Fa-f]\{2\}\).*$/\1/p")
+macaddr=$(sed -n "s/^.*androidboot\.wifimacaddr=\(\([0-9A-Fa-f]\{2\}:\)\{5\}[0-9A-Fa-f]\{2\}\).*$/\1/p" < /proc/cmdline)
 
-/sbin/ip link set wlan0 address $macaddr
+/sbin/ip link set wlan0 address "$macaddr"