Hexagon (target/hexagon) Additional instructions handled by idef-parser

Hexagon (target/hexagon) Additional instructions handled by idef-parser

**** Changes in v3 ****
Fix bugs exposed by dpmpyss_rnd_s0 instruction
    Set correct size/signedness for constants
    Test cases added to tests/tcg/hexagon/misc.c

**** Changes in v2 ****
Fix bug in imm_print identified in clang build

Currently, idef-parser skips all floating point instructions.  However,
there are some floating point instructions that can be handled.

The following instructions are now parsed
    F2_sfimm_p
    F2_sfimm_n
    F2_dfimm_p
    F2_dfimm_n
    F2_dfmpyll
    F2_dfmpylh

To make these instructions work, we fix some bugs in parser-helpers.c
    gen_rvalue_extend
    gen_cast_op
    imm_print
    lexer properly sets size/signedness of constants

Test cases added to tests/tcg/hexagon/fpstuff.c

Signed-off-by: Taylor Simpson <tsimpson@quicinc.com>
Tested-by: Anton Johansson <anjo@rev.ng>
Reviewed-by: Anton Johansson <anjo@rev.ng>
Message-Id: <20230501203125.4025991-1-tsimpson@quicinc.com>