pine64-pinephone: fix pre-upgrade script (MR 2512)

Use -f, so rm
* does not complain if the file does not exist
* does not exit with 1 if the file does not exist

Remove the stdout/stderr redirect (not needed with -f).

Add exit 0 at the end of the file, even though it clearly should not
exit with anything other than 0 anymore, as it's common practice in
these pre-upgrade etc. scripts.

With the old script, the problem was that it would exit 1 as soon as the
files did not exist at the time the script runs. Exit 1 in this
pre-upgrade script causes apk to show an error, and it would not go away
with 'apk fix' since it ran into the same problem.

Fixes: 7c511d ("pine64-pinephone: remove old u-boot...")

device/main/device-pine64-pinephone/APKBUILD

@@ -6,7 +6,7 @@
 # Co-Maintainer: Dylan Van Assche <me@dylanvanassche.be>
 pkgname=device-pine64-pinephone
 pkgver=0.35
-pkgrel=1
+pkgrel=2
 pkgdesc="PINE64 PinePhone"
 url="https://postmarketos.org"
 license="MIT"

device/main/device-pine64-pinephone/device-pine64-pinephone.pre-upgrade

@@ -4,5 +4,7 @@
 # packaging so remove them here to prevent a failed upgrade if /boot is too
 # full
 # see: https://gitlab.com/postmarketOS/pmaports/-/merge_requests/2449
-rm /boot/uImage-postmarketos-allwinner 2>/dev/null 1>&2
-rm /boot/uInitrd-postmarketos-allwinner 2>/dev/null 1>&2
+rm -f /boot/uImage-postmarketos-allwinner
+rm -f /boot/uInitrd-postmarketos-allwinner
+
+exit 0