arm: async uart writes & fixes

arm/makefile

@@ -23,7 +23,7 @@ includes += -Ihal/lib/common
 sources += hal/uart/xuartlite.c hal/uart/xuartlite_stats.c hal/uart/xuartlite_intr.c
 includes += -Ihal/uart
 
-bootloader_objects = uart.o bootloader.o vector_table.o $(sources:.c=.o)
+bootloader_objects = bootloader.o vector_table.o $(sources:.c=.o)
 app_objects = app_init.o crash.o main.o uart.o stdlib.o async.o trace.o $(sources:.c=.o)
 
 CPPFLAGS += $(includes)