radeonsi: load the right number of components for VS inputs and TBOs

radeonsi: load the right number of components for VS inputs and TBOs

The supported counts are 1, 2, 4. (3=4)

The following snippet loads float, vec2, vec3, and vec4:

Before:
    buffer_load_format_x v9, v4, s[0:3], 0 idxen          ; E0002000 80000904
    buffer_load_format_xyzw v[0:3], v5, s[8:11], 0 idxen  ; E00C2000 80020005
    s_waitcnt vmcnt(0)                                    ; BF8C0F70
    buffer_load_format_xyzw v[2:5], v6, s[12:15], 0 idxen ; E00C2000 80030206
    s_waitcnt vmcnt(0)                                    ; BF8C0F70
    buffer_load_format_xyzw v[5:8], v7, s[4:7], 0 idxen   ; E00C2000 80010507

After:
    buffer_load_format_x v10, v4, s[0:3], 0 idxen         ; E0002000 80000A04
    buffer_load_format_xy v[8:9], v5, s[8:11], 0 idxen    ; E0042000 80020805
    buffer_load_format_xyzw v[0:3], v6, s[12:15], 0 idxen ; E00C2000 80030006
    s_waitcnt vmcnt(0)                                    ; BF8C0F70
    buffer_load_format_xyzw v[3:6], v7, s[4:7], 0 idxen   ; E00C2000 80010307

Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>