Without that change booting leads to crash with more warnings like below:
[    0.284454] omap_hwmod: uart4: cannot clk_get main_clk uart4_fck
[    0.284484] omap_hwmod: uart4: cannot _init_clocks
[    0.284484] ------------[ cut here ]------------
[    0.284545] WARNING: CPU: 0 PID: 1 at arch/arm/mach-omap2/omap_hwmod.c:2543 _init+0x300/0x3e4()
[    0.284545] omap_hwmod: uart4: couldn't init clocks
[    0.284576] Modules linked in:
[    0.284606] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.13.0-next-20140124-00020-gd2aefec-dirty #26
[    0.284637] [<c00151c0>] (unwind_backtrace) from [<c0011e20>] (show_stack+0x10/0x14)
[    0.284667] [<c0011e20>] (show_stack) from [<c0568544>] (dump_stack+0x7c/0x94)
[    0.284729] [<c0568544>] (dump_stack) from [<c003ff94>] (warn_slowpath_common+0x6c/0x90)
[    0.284729] [<c003ff94>] (warn_slowpath_common) from [<c003ffe8>] (warn_slowpath_fmt+0x30/0x40)
[    0.284759] [<c003ffe8>] (warn_slowpath_fmt) from [<c07d1be8>] (_init+0x300/0x3e4)
[    0.284790] [<c07d1be8>] (_init) from [<c07d217c>] (__omap_hwmod_setup_all+0x40/0x8c)
[    0.284820] [<c07d217c>] (__omap_hwmod_setup_all) from [<c0008918>] (do_one_initcall+0xe8/0x14c)
[    0.284851] [<c0008918>] (do_one_initcall) from [<c07c5c18>] (kernel_init_freeable+0x104/0x1c8)
[    0.284881] [<c07c5c18>] (kernel_init_freeable) from [<c0563524>] (kernel_init+0x8/0x118)
[    0.284912] [<c0563524>] (kernel_init) from [<c000e368>] (ret_from_fork+0x14/0x2c)
[    0.285064] ---[ end trace 63de210ad43b627d ]---

Reference:
https://lkml.org/lkml/2013/10/8/553Signed-off-by: Marek Belisko <marek@goldelico.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>