oniro-linux: use grub-efi as EFI_PROVIDER

Prefer GRUB as the EFI provider.

The SysOTA+RAUC stack supports GRUB as the point of integration. This is
caused by both RAUC downstream support for GRUB and GRUB's ability to
load the kernel from a squashfs image.

In addition, add TODO about GRUB and microcode updates

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@huawei.com>

meta-oniro-core/conf/distro/oniro-linux.conf

@@ -81,6 +81,16 @@ PREFERRED_PROVIDER_virtual/kernel:qemux86-64 = "linux-oniro"
 # When kernel version is bumped we will have to revisit here.
 PREFERRED_PROVIDER_virtual/kernel_qemu-generic-arm64 = "linux-oniro"
 
+# Prefer GRUB as the EFI provider.
+#
+# The SysOTA+RAUC stack supports GRUB as the point of integration. This is
+# caused by both RAUC downstream support for GRUB and GRUB's ability to load the
+# kernel from a squashfs image.
+#
+# FIXME: allow GRUB to update the CPU microcode
+# https://booting.oniroproject.org/distro/oniro/-/issues/247
+EFI_PROVIDER = "grub-efi"
+
 # qemu-generic-arm64 specific requirements
 PREFERRED_VERSION_optee-os:qemu-generic-arm64 = "3.14.0"