microblaze: Enable options to mount a rootfs via NFS

Enable the options to mount a rootfs over NFS for microblaze
platforms and also support for automatic configuration of IP addresses
during boot as needed by NFS.
Signed-off-by: Raju Kumar Pothuraju <rajukumar.pothuraju@amd.com>
Reviewed-by: Radhey Shyam Pandey <radhey.shyam.pandey@amd.com>
Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/d7bc1c93e485e0a6ab2c234a144402b7bd5f77bb.1698155190.git.michal.simek@amd.com

arch/microblaze/configs/mmu_defconfig

@@ -25,6 +25,10 @@ CONFIG_NET=y
 CONFIG_PACKET=y
 CONFIG_UNIX=y
 CONFIG_INET=y
+CONFIG_IP_PNP=y
+CONFIG_IP_PNP_DHCP=y
+CONFIG_IP_PNP_BOOTP=y
+CONFIG_IP_PNP_RARP=y
 # CONFIG_IPV6 is not set
 CONFIG_BRIDGE=m
 CONFIG_PCI=y
@@ -74,6 +78,7 @@ CONFIG_TMPFS=y
 CONFIG_CRAMFS=y
 CONFIG_ROMFS_FS=y
 CONFIG_NFS_FS=y
+CONFIG_ROOT_NFS=y
 CONFIG_CIFS=y
 CONFIG_ENCRYPTED_KEYS=y
 CONFIG_DMA_CMA=y