sdm845: remove TARGET_BOARD_PLATFORM

This was pulling in some ancient qualcomm HALs which don't build anymore
diff --git a/sdm845/BoardConfig.mk b/sdm845/BoardConfig.mk
index bacbc2e..f6a9935 100644
--- a/sdm845/BoardConfig.mk
+++ b/sdm845/BoardConfig.mk
@@ -3,7 +3,7 @@
 # Copied from https://github.com/LineageOS/android_device_oneplus_sdm845-common/blob/lineage-16.0/BoardConfigCommon.mk
 # Board Information
 TARGET_BOOTLOADER_BOARD_NAME := sdm845
-TARGET_BOARD_PLATFORM := sdm845
+#TARGET_BOARD_PLATFORM := sdm845
 
 # Kernel/boot.img Configuration
 BOARD_KERNEL_BASE        := 0x00000000