host: Don't pass -1 (converted to 255) as address

We initialize a local variable to -1, and if the user specifies
no address from the command line, we use this in the interface match
struct, which uses a uint8_t.  This means 255 ends up in there, and
as a result no usb interface ever matches unless the user explicitly
specifies the -A command line argument.

With this patch any absent -A argument will result in ifm.addr == 0,
which means "don't match on address", and which is what we want here.

Change-Id: Iffb5fa406ddef00c7c15570ffca2c109b98d7a2d
---
M host/src/simtrace2-cardem-pcsc.c
M host/src/simtrace2-tool.c
2 files changed, 4 insertions(+), 2 deletions(-)