net: Kirkwood_egiga.c: fixed build warnings

This patch fixes following build warnings for kirkwood_egiga.c

kirkwood_egiga.c: In function "kwgbe_init":
kirkwood_egiga.c:448: warning: dereferencing type-punned pointer will break strict-aliasing rules
kirkwood_egiga.c: In function "kwgbe_recv":
kirkwood_egiga.c:609: warning: dereferencing type-punned pointer will break strict-aliasing rules

Signed-off-by: Prafulla Wadaskar <prafulla@marvell.com>
Signed-off-by: Ben Warren <biggerbadderben@gmail.com>