media: ir-kbd-i2c: change the if logic to avoid a warning

While the code is correct, it produces this warning:
	drivers/media/i2c/ir-kbd-i2c.c:593 zilog_ir_format() error: buffer overflow 'code_block->codes' 61 <= 173

As static analyzers may be tricked by arithmetic expressions on
comparisions. So, change the order, in order to shut up this
false-positive warning.

That also makes easier for humans to understand that it won't
be trying to go past buffer size.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>