main/postmarketos-initramfs: wait for boot partition

Some devices take time to initialize storage, e.g. Qualcomm laptops using ADSP need to load firmware firstly, and initramfs script does not always manage to mount boot partition in time.

Unfortunately, there is no reliable way to reproduce the issue, but this patch should fix cases like this.

main/postmarketos-initramfs/APKBUILD

 # Maintainer: Oliver Smith <ollieparanoid@postmarketos.org>
 # Co-Maintainer: Clayton Craft <clayton@craftyguy.net>
 pkgname=postmarketos-initramfs
-pkgver=2.5.0
+pkgver=2.5.1
 pkgrel=0
 pkgdesc="Base files for the postmarketOS initramfs / initramfs-extra"
 url="https://postmarketos.org"
@@ -87,8 +87,8 @@ sha512sums="
 5b364300f31c91fd0591eb0715f67cbf5383f45246a5fb9f34b79f7cb2e3b15768b2130e5f32f816cc169950f988c1beabc879ba31645c58ce131a288dbc071d  00-initramfs-base.dirs
 ab41b45b0613f25a61114ed8c8b92bc53c60838f6e2e0ba18c76e5369b2984e6023a0661887692673aca3f647f268c468a468f6b1ac424cfee609017a89481dd  00-initramfs-base.files
 8a4adad3785af474b36a09a05f6a3b2c4b4f43aac331a53b903abfa51ea12be1e3d1d807b7a6e66a1346815f3b0044daf8cd62e21e2dc75d2db13ee265a72985  00-initramfs-extra-base.files
-4bfcb41b2d5ccd577a6203a9479e5bdf056064d20f02f9120f1a074c7c280c0231cf380ed6be7c80733ed4ae101385c14f123a8a41780bbb7d0851387cd9c613  init.sh
-87602909fa9f233385528e41e5395cce076a4d22df858b56b333457815c6978f1b9ca918f0c9ec56f4424ed6c2624d0c6054eaf6e687d60175952cc35c010098  init_functions.sh
+b1462989633c65a102e7ae7ced9c41a00673b4c7434cd3fe16c229c39bb870d7e850b0d317487191b7d7ca32c75b2eed1561b1facf405bd4d876d32c71badcf3  init.sh
+9c7225abc312342b1aab55b9619a504bb58f51d9c09700bf5b57e03327d5792aafea1d5086701199501e76b94b22b7f112ca39be537ade773eef107d7bae113a  init_functions.sh
 ba3275a9af788c7c782322a22a0f144d5e50e3498ea6886486a29331f23ae89cd32d500a3635cfa7cab369afba92edc18aeca64ccbf0cd589061cce23d15b46c  unudhcpd.conf
 675e7d5bee39b2df7d322117f8dcaccc274d61beaf4d50ead19bbf2109446d64b1c0aa0c5b4f9846eb6c1c403418f28f6364eff4537ba41120fbfcbc484b7da7  mdev.conf
 "