CSN1 decoding: add test to show bug in CSN_LEFT_ALIGNED_VAR_BMP

CSN1 decoding currently contains an attempted read past vector boundaries in
case of a starting bit offset != 0, so that the last amount of bits read should
be < 8. In the case of CSN_LEFT_ALIGNED_VAR_BMP, the mod-8 calculation is
flawed, and in what should be the final step of reading n < 8 bits, 8 bits are
read instead of n (with an extraneous read of n bits following after that).
This leads to -EINVAL being returned by bitvec_get_bit_pos() and bogus
resulting data.

Add testCsnLeftAlignedVarBmpBounds() in RLCMACTest.cpp to show and expect this
bug. The test's expectation shall be corrected along with the bug fix in a
subsequent commit.

Related: OS#1805
Tweaked-by: Neels Hofmeyr <nhofmeyr@sysmocom.de>
Change-Id: I4641f5d1d49f66cb1a5cd813befb3a2a266001b0
1 file changed