[NVPTX] fix ptr handling and 'byval' arg replacement in NVPTXLowerArgs#20924

bratpiorka wants to merge 2 commits intointel:syclintel/llvm:syclfrom

bratpiorka:rrudnick_fix_nvptx_lowerbratpiorka/llvm:rrudnick_fix_nvptx_lowerCopy head branch name to clipboard