firmware-samsung-maguro: update arch to armv7

I've updated the samsung-maguro packages to armv7 some time ago and forgot about the firmware package

firmware/firmware-samsung-maguro/APKBUILD

 pkgname=firmware-samsung-maguro
 pkgver=1
-pkgrel=0
+pkgrel=1
 pkgdesc="Google Galaxy Nexus (GSM) Firmware"
 url="https://postmarketos.org"
-arch="armhf"
+arch="armv7"
 license="proprietary"
 depends="firmware-aosp-broadcom-wlan"
 options="!check !strip"