This issue has been resolved. DSI panel is appearing in both LK stage and after the Linux kernel boots up.
But now, what happens is : when we do hard reboot, in LK stage the backlight is ON but no image is displayed.
whereas when we do Soft reboot (from command line) image is displayed in the LK.
The following is the boot sequence which is same in both the cases:
, ++++++++++++++++func:gcdb_display_init, line:376
 ++++++++++++++++++ hw_id:24, line:486, func:oem_panel_select, panel_name:ssd2080m_720p_video
 OEM panel override:ssd2080m_720p_video
 +++++++++++line:439 func:init_panel_data
 +++++++++++++++++func: init_platform_data line:291
 ++++++++++++++++++++func:msm_display_init, line:241
 +++++++++++++++++++++func:msm_display_init, LINE:279
 +++++++++++++++++++++func:msm_fb_alloc, LINE:42
 +++++++++++++++++++++func:msm_display_init, LINE:284
 +++++++++++++++++++++func:fbcon_setup, LINE:178
 +++++++++++++++++++++func:display_image_on_screen, LINE:224
 +++++++++++++++++++++func:fbcon_clear, LINE:124
 +++++++++++++++++++++func:fetch_image_from_partition, LINE:2778
 +++++++++++++++++++++func:splash_screen_mmc, LINE:2727
 +++++++++++++++++++++func:splash_screen_mmc, LINE:2734
 ERROR: splash Partition invalid
 +++++++++++++++++++++func:fbcon_putImage, LINE:255
 +++++++++++++++++++++func:fbcon_flush, LINE:94
 Config MIPI_VIDEO_PANEL.
 ++++++++++++++++++++func:mdss_dsi_panel_initialize, line:513
 ++++++++++++++++++++func:msm_display_on, line:148
 Turn on MIPI_VIDEO_PANEL.
 ++++++++++++++++++++func:mdss_dsi_post_on, line:818
 Video lane tested successfully
If anyone can please help me in this.