Most GMSL devices have one address. This is a serializer so the default (with ADD pins set low – see Table 1) is address 0x80.
The MAX9291/3 are different. The HDMI blocks in these parts, are addressed as separate devices, so in Table 33 I2C Address 0xA0 means you talk to these HDMI Registers by addressing device 0xA0 and then the appropriate register.