lib: aarch64: fix non-code symbol errors flagged by armlink
This patch modifies the code to turn __1printf and __2printf into proper
functions to fix the following errors flagged by armlink.
Error: L6318W: backtrace.o(.text.backtrace) contains branch to a non-code symbol __2printf.
Error: L6318W: backtrace.o(.text.backtrace) contains branch to a non-code symbol __2printf.
Error: L6318W: backtrace.o(.text.backtrace) contains branch to a non-code symbol __2printf.
Error: L6318W: backtrace.o(.text.backtrace) contains branch to a non-code symbol __2printf.
Error: L6318W: backtrace.o(.text.backtrace) contains branch to a non-code symbol __2printf.
Error: L6318W: backtrace.o(.text.backtrace) contains branch to a non-code symbol __2printf.