Add aarch64 support

[Mabbs]

Fixed #93
Tested on Raspberry Pi 3b and 4b.

[ellartdev]

Wouldn't this be better, as there are multiple revisions of RPi 4 Model B boards? Multiple revisions (i.e. I have Revision 1.5, PCPUI variable outputs 15), but CPU is the same. My example below:

...
LSCPU := $(shell lscpu | grep "Model name" | awk '{print $$3}')
...
...
else ifeq ($(UNAME), aarch64)
	ifeq ($(LSCPU), Cortex-A72)
		CFLAGS = $(STD_CFLAGS) -march=armv8-a -mtune=cortex-a72 -ffast-math -DRASPI=4
		TARGET = pi4
	else
		CFLAGS = $(STD_CFLAGS) -march=armv7-a -ffast-math -DRASPI=2
		TARGET = pi2
	endif
else
	CFLAGS = $(STD_CFLAGS)
	TARGET = other
endif
...

[Mabbs]

Wouldn't this be better, as there are multiple revisions of RPi 4 Model B boards? Multiple revisions (i.e. I have Revision 1.5, PCPUI variable outputs 15), but CPU is the same. My example below:

...
LSCPU := $(shell lscpu | grep "Model name" | awk '{print $$3}')
...
...
else ifeq ($(UNAME), aarch64)
	ifeq ($(LSCPU), Cortex-A72)
		CFLAGS = $(STD_CFLAGS) -march=armv8-a -mtune=cortex-a72 -ffast-math -DRASPI=4
		TARGET = pi4
	else
		CFLAGS = $(STD_CFLAGS) -march=armv7-a -ffast-math -DRASPI=2
		TARGET = pi2
	endif
else
	CFLAGS = $(STD_CFLAGS)
	TARGET = other
endif
...

You're right, I modified.