tty: gdm724x: use min_t() for size_t varable and a constant

My thinking was that ulong is the same as size_t everywhere. No, size_t
is uint on 32bit. So the below commit introduced a build warning on
32bit:
.../gdm724x/gdm_tty.c:165:24: warning: comparison of distinct pointer types ('typeof (2048UL) *' (aka 'unsigned long *') and 'typeof (remain) *' (aka 'unsigned int *'))

To fix this, partially revert the commit (remove constants' suffixes)
and switch to min_t() in this case instead.

/me would hope for Z (or alike) suffix for constants.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Fixes: c3e5c706 (tty: gdm724x: convert counts to size_t)
Reported-by: Nathan Chancellor <nathan@kernel.org>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202308151953.rNNnAR2N-lkp@intel.com/


Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Tested-by: Nathan Chancellor <nathan@kernel.org> # build
Link: https://lore.kernel.org/r/20230816085322.22065-1-jirislaby@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>