hdmitx: fix wrong kmalloc usage

hdmitx: fix wrong kmalloc usage

PD#161652: fix wrong kmailloc(, GFP_KERNEL) usage
At timer function. System will throw
    [<ffffff800908a0d8>] dump_backtrace+0x0/0x1d0
    [<ffffff800908a2cc>] show_stack+0x24/0x30
    [<ffffff8009465c60>] dump_stack+0x90/0xb0
    [<ffffff80090cc2e4>] ___might_sleep+0x14c/0x1a0
    [<ffffff80090cc394>] __might_sleep+0x5c/0x98
    [<ffffff80091e4ecc>] kmem_cache_alloc_trace+0x1ec/0x238
    [<ffffff800979d18c>] hdcptx_events_handle+0x45c/0x640
    [<ffffff800911193c>] call_timer_fn+0x3c/0x1b0
    [<ffffff8009111bb8>] expire_timers+0xd8/0x178
    [<ffffff8009111cec>] run_timer_softirq+0x94/0x178
    [<ffffff800908183c>] __do_softirq+0x12c/0x344
    [<ffffff80090a5344>] irq_exit+0xa4/0xd0
    [<ffffff80090fc8d8>] __handle_domain_irq+0x90/0x100
    [<ffffff800908154c>] gic_handle_irq+0x5c/0xb0
Should use GFP_ATOMIC instead.

Change-Id: I70778a6e3d993d87f71be208503688286913bda1
Signed-off-by: Zongdong Jiao <zongdong.jiao@amlogic.com>