gdb: fix -Wtautological-overlap-compare error in lm32-tdep.c

gdb: fix -Wtautological-overlap-compare error in lm32-tdep.c

Building with clang 11, we get:

    /home/smarchi/src/binutils-gdb/gdb/lm32-tdep.c:84:44: error: overlapping comparisons always evaluate to false [-Werror,-Wtautological-overlap-compare]
        return ((regnum >= SIM_LM32_EA_REGNUM) && (regnum <= SIM_LM32_BA_REGNUM))
                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Indeed, this doesn't make sense, as EA_REGNUM is greater than BA_REGNUM.
I'll assume that it was just a mistake and that these two should be
swapped.

The regnums for BA and EA are contiguous, so ultimately this particular
part of the condition is only true if regnum is == EA or == BA.  These
registers are Exception Address and Breakpoint Address, so I guess it
makes sense for them to be in the system register group.

The relevant reference is here:

  https://www.latticesemi.com/-/media/LatticeSemi/Documents/UserManuals/JL/LatticeMico32ProcessorReferenceManual39.ashx?document_id=52077

gdb/ChangeLog:

	* lm32-tdep.c (lm32_register_reggroup_p): Fix condition.