Uses bytearray.fromhex which isn't in CircuitPython

[dastels]

There are two calls to bytearray.fromhex in adafruit_atecc.py but bytearray doesn't support/include a fromhex method in CircuitPython.

`CFG_TLS = bytes(
bytearray.fromhex(
"01 23 00 00 00 00 50 00 00 00 00 00 00 c0 71 00"
"20 20 20 20 20 20 20 20 20 20 20 20 20 c0 00 55"
"00 83 20 87 20 87 20 87 2f 87 2f 8f 8f 9f 8f af"
"20 20 20 20 20 20 20 20 20 20 20 20 20 8f 00 00"
"00 00 00 00 00 00 00 00 00 00 00 00 20 20 20 20"
"20 20 20 20 20 20 20 20 20 af 8f ff ff ff ff 00"
"00 00 00 ff ff ff ff 00 20 20 20 20 20 20 20 20"
"20 20 20 20 20 00 00 00 ff ff ff ff ff ff ff ff"
"ff ff ff ff 20 20 20 20 20 20 20 20 20 20 20 20"
"20 ff ff ff ff 00 00 55 55 ff ff 00 00 00 00 00"
"00 33 20 20 20 20 20 20 20 20 20 20 20 20 20 00"
"33 00 33 00 33 00 33 00 1c 00 1c 00 1c 00 3c 00"
"3c 00 3c 00 3c 20 20 20 20 20 20 20 20 20 20 20"
"20 20 00 3c 00 3c 00 3c 00 1c 00"
)
)

_CFG_BYTES_LIST = list(bytearray(CFG_TLS))
_CFG_BYTE_16 = bytes(bytearray.fromhex(hex(_I2C_ADDR << 1).replace("0x", "")))`

[ladyada]

@dastels ok please submit a PR

[silvester]

This should be fixed with the latest commit.