media: lgdt3306a: Add a check against null-pointer-def

media: lgdt3306a: Add a check against null-pointer-def

The driver should check whether the client provides the platform_data.

The following log reveals it:

[   29.610324] BUG: KASAN: null-ptr-deref in kmemdup+0x30/0x40
[   29.610730] Read of size 40 at addr 0000000000000000 by task bash/414
[   29.612820] Call Trace:
[   29.613030]  <TASK>
[   29.613201]  dump_stack_lvl+0x56/0x6f
[   29.613496]  ? kmemdup+0x30/0x40
[   29.613754]  print_report.cold+0x494/0x6b7
[   29.614082]  ? kmemdup+0x30/0x40
[   29.614340]  kasan_report+0x8a/0x190
[   29.614628]  ? kmemdup+0x30/0x40
[   29.614888]  kasan_check_range+0x14d/0x1d0
[   29.615213]  memcpy+0x20/0x60
[   29.615454]  kmemdup+0x30/0x40
[   29.615700]  lgdt3306a_probe+0x52/0x310
[   29.616339]  i2c_device_probe+0x951/0xa90

Link: https://lore.kernel.org/linux-media/20220405095018.3993578-1-zheyuma97@gmail.com
Signed-off-by: Zheyu Ma <zheyuma97@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>