tizen: bootscript: vf2: Set eth0 ip addr only for flash boot mode

tizen: bootscript: vf2: Set eth0 ip addr only for flash boot mode

The visionfive2 board has two ethernet interfaces and setting
ipaddr without intercace, it tries all interface for all enabled
autoconfiguration protocol. Sometimes, this causes boot hang to
get recv from an ethernet interface for an autoconfiguration
protocol. To remove the possible boot hang, set only eth0 ip addr
for flash boot mode.

Refer "ip=" part of below kernel doc:
  https://git.tizen.org/cgit/platform/kernel/linux-starfive/tree/Documentation/admin-guide/nfs/nfsroot.rst?h=tizen

Change-Id: Ia927d2e64945ef9cc48685e4640c9f366898eb6e
Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>