eepro100: initialize a variable in all cases

Compiling with GCC 4.6.0 20100925 produced warnings:
/src/qemu/hw/eepro100.c: In function 'eepro100_read4':
/src/qemu/hw/eepro100.c:1351:14: error: 'val' may be used uninitialized in this function [-Werror=uninitialized]
/src/qemu/hw/eepro100.c: In function 'eepro100_read2':
/src/qemu/hw/eepro100.c:1328:14: error: 'val' may be used uninitialized in this function [-Werror=uninitialized]
/src/qemu/hw/eepro100.c: In function 'eepro100_read1':
/src/qemu/hw/eepro100.c:1285:13: error: 'val' may be used uninitialized in this function [-Werror=uninitialized]

Fix by initializing 'val' at start.

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
