arm64: Enable CONFIG_KEXEC_FILE (sonic-net#333)

This change enables CONFIG_KEXEC_FILE to make kexec_file_load() system
call available. This functionality is needed for warm-reboot support.

Change-Id: Iaf10e1a153bbac2e344d0c9646e7fa1fe5f7429d

Signed-off-by: Pavan Naregundi <[email protected]>

Author: pavannaregundi

patch/kconfig-inclusions

@@ -193,6 +193,7 @@ CONFIG_SPI_DW_MMIO=m
 CONFIG_SQUASHFS_DECOMP_MULTI=y
 CONFIG_PREEMPTIRQ_TRACEPOINTS=y
 CONFIG_RING_BUFFER_ALLOW_SWAP=y
+CONFIG_KEXEC_FILE=y
 
 [marvell-arm64]
 CONFIG_MARVELL_AC5_WATCHDOG=m