sd/sd.c: Fix "inquiry" ACMD41

sd/sd.c: Fix "inquiry" ACMD41

QEMU models two (of the three) ACMD41 has two modes, "inquiry" and
"first". The selection logic for which of the two is incorrect - it
compares != 0 for the entire argument value rather than only bits 23:0
as per the spec. Fix.

Signed-off-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Message-id: 3ef0a7fd1b2f3ebb23b4fdeabcc14caf3fad6d71.1369622254.git.peter.crosthwaite@xilinx.com
Reviewed-by: Igor Mitsyanko <i.mitsyanko@gmail.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>