i965/fs: Add byte scattered read message and fs support

i965/fs: Add byte scattered read message and fs support

v2: Fix alignment style (Topi Pohjolainen)
    (Jason Ekstrand)
    - Enable bit_size parameter to scattered messages to enable different
      bitsizes byte/word/dword.
    - Remove use of brw_send_indirect_scattered_message in favor of
      brw_send_indirect_surface_message.
    - Move scattered messages to surface messages namespace.
    - Assert align1 for scattered messages and assume Gen8+.
    - Inline brw_set_dp_byte_scattered_read.

v3: (Jason Ekstrand)
    - Use renamed brw_byte_scattered_data_element_from_bit_size method
    - Assert scattered read for Gen8+ and Haswell.
    - Use conditional expresion at components_read.
    - Include comment about params for scattered opcodes.

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>