poplar: misc updates needed for Linux 5.5

1. Drop workarounds for GCC 8.x
2. Provide eMMC as env variable, which is used in extlinux.conf
distroboot script.
3. Use default defconfig for all arm64.
4. Merge additional poplar.conf

Acked-by: Jerome Forissier <jerome@forissier.org>
Signed-off-by: Igor Opaniuk <igor.opaniuk@gmail.com>

poplar.mk

@@ -132,16 +132,12 @@ l-loader-clean:
 ################################################################################
 LINUX_DEFCONFIG_COMMON_ARCH := arm64
 LINUX_DEFCONFIG_COMMON_FILES := \
-		$(LINUX_PATH)/arch/arm64/configs/poplar_defconfig \
+		$(LINUX_PATH)/arch/arm64/configs/defconfig \
+		$(CURDIR)/kconfigs/poplar.conf
 
 linux-defconfig: $(LINUX_PATH)/.config
 
 LINUX_COMMON_FLAGS += ARCH=arm64
-# Avoid compile errors with GCC 8.x. These flags may be removed when
-# https://github.com/96boards-poplar/linux/pull/3 is merged.
-LINUX_COMMON_FLAGS += CFLAGS_drv_hifb_proc.o=-Wno-stringop-truncation \
-		      CFLAGS_drv_pvr_intf.o=-Wno-sizeof-pointer-memaccess \
-		      CFLAGS_drv_display.o=-Wno-array-bounds
 
 linux: linux-common
 
@@ -163,7 +159,8 @@ prepare-images: linux l-loader buildroot
 	@cp $(LINUX_PATH)/arch/arm64/boot/Image $(OUT_PATH)
 	@cp $(LINUX_DTB) $(OUT_PATH)
 	@cd $(OUT_PATH) && PATH=$(UBOOT_PATH)/tools:$$PATH \
-	       bash ./poplar_recovery_builder.sh all "$(ROOTFS_BIN)"
+	       EMMC_DEV=/dev/mmcblk1 ./poplar_recovery_builder.sh \
+	       all "$(ROOTFS_BIN)"
 
 ################################################################################
 # Buildroot/RootFS