[AMDGPU][MC][GFX10] MIMG gather4 opcodes failed to disassemble when d16 is specified

[dpreobra]

Bugzilla Link	51723
Version	trunk
OS	Windows NT

Extended Description

An example of failed test:

0x08,0x08,0x00,0xf1,0x01,0xfe,0x62,0x80

Expected output:

image_gather4 v[254:255], v[1:2], s[8:15], s[12:15] dmask:0x8 dim:SQ_RSRC_IMG_2D d16

Actual result:

s_add_u32 s98, s1, src_lds_direct ; encoding: [0x01,0xfe,0x62,0x80]

Note that instruction image_gather4 shown above is assembled fine with expected encoding but this encoding cannot be disassembled.

[dpreobra]

assigned to @dpreobra