broadcom/vc5: Emit flat shade flags for varying components > 24.

broadcom/vc5: Emit flat shade flags for varying components > 24.

This means that with no flatshading we'll emit the single-byte
ZERO_ALL_FLAT_SHADE_FLAGS, and otherwise emit a set of FLAT_SHADE_FLAGS to
get all the bits we need set.

There's a _SET enum in the packet we could use to possibly set entire
ranges of the bitfield without using another packet, but this at least
fixes the conformance failure.