qemu-traditional: Fix build warnings on Wheezy

qemu-traditional: Fix build warnings on Wheezy

  CC    i386-dm/eepro100.o
hw/eepro100.c: In function ‘eepro100_read4’:
hw/eepro100.c:1232:5: warning: ‘val’ may be used uninitialized in this function [-Wmaybe-uninitialized]
hw/eepro100.c: In function ‘eepro100_read2’:
hw/eepro100.c:1202:5: warning: ‘val’ may be used uninitialized in this function [-Wmaybe-uninitialized]
hw/eepro100.c: In function ‘eepro100_read1’:
hw/eepro100.c:1179:5: warning: ‘val’ may be used uninitialized in this function [-Wmaybe-uninitialized]

Use ~0 to match the behaviour of real hardware.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
CC: Ian Campbell <Ian.Campbell@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>