SparcInstPrinter: Support llvm-objdump --print-imm-hex
... to align with other targets, e.g., https://reviews.llvm.org/D77853
(AArch64) and https://reviews.llvm.org/D83634 (AVR).
binutils's sparc port uses %d when imm<=9, diverging from other ports.
We do not follow the binutils sparc port behavior.
