selftests: vDSO: remove unnecessary command line defs from chacha test

CONFIG_FUNCTION_ALIGNMENT=0 is no longer necessary and BULID_VDSO wasn't
spelled right while BUILD_VDSO isn't necessary, so just remove these.

Reported-by: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>