{linux-postmarketos-allwinner,linux-purism-librem5}: restore CMA size

This partly reverts the commit mentioned below. When disabling CMA I thought that libcamera was the only user of it, which is only true for userspace, though. In fact CMA is used and often even required by the kernel for HW video decoders, display engines and other hardware that might not have a MMU.

Thus restore the previously established value.

Fixes: 196ece02 (linux-postmarketos-allwinner: enable CONFIG_UDMABUF (MR 5585)) Fixes: d53e8a7e (linux-purism-librem5: enable CONFIG_UDMABUF (MR 5584))

---

Sorry for not researching this directly - TIL a lot :) Note that this might explain issues we're seeing on other devices as well. Values like 256MB will often not be enough to allocate the required number of buffers by modern codecs for 4K@60FPS - and a bunch of other devices don't have CMA enabled in the first place. But that need further investigations.

device/main/linux-postmarketos-allwinner/APKBUILD

@@ -81,7 +81,7 @@ package() {
 }
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 a1fe1a21c34062eb92b6a4a9d2ef330d0e745859af283ccf05fc899ec263f9d452c1399c29620a0e4c748eca4b0c13645668b2fc0dc72f5703426d472f1294be  0001-dts-add-dontbeevil-pinephone-devkit.patch
 0ef26b34fa834c119ebff6daa27b1dd3fac27448d6a40c0b2022a00c239dad0ef3e2b3ab3f9eec5460f921c9c6ea21db360adc175a7e658d5c34c5d0aacc498f  0002-dts-add-pinetab-dev-old-display-panel.patch