Move the BR_TRANSACTION_SEC_CTX debug string

It will end up in the same index as BR_TRANSACTION because they are
both defined as reply 2 with the only difference being the size of the
structs which is stored in the lower 14 bits of the top 16 bits of the
32-bit structure. When we index into this array, we use only the bottom
8 bits with _IOC_NRBITS.

See the definition in bionic/libc/kernel/uapi/linux/android/binder.h

Test: m
Bug: none
Change-Id: Ie301d1fd89085dc69a2966b0f3ca349732133f8f