i2c_helper_linux.c: Use a fixed-size buffer

Given that the buffer size is known in advance, using malloc() is not
necessary. To avoid open-coding buffer sizes, add some trailing null
characters to `I2C_DEV_PREFIX`, as placeholders for bus number digits.
Finally, replace the now-unnecessary `goto` statements with `return`.

Change-Id: I6060749c6ded10949344caee3cc3943306e74a1c
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/52415
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
1 file changed