LoongArch: Fix tst-gnu2-tls2 test case

asm volatile ("movfcsr2gr $t0, $fcsr0" ::: "$t0");
asm volatile ("st.d $t0, %0" :"=m"(restore_fcsr));

generate to the following instructions with -Og flag:

movfcsr2gr      $t0, $zero
addi.d          $t0, $sp, 2047(0x7ff)
addi.d          $t0, $t0, 77(0x4d)
st.w            $t0, $t0, 0

fcsr0 register and restore_fcsr variable are both stored in t0 register.

Change to:

asm volatile ("movfcsr2gr %0, $fcsr0" :"=r"(restore_fcsr));

to avoid restore_fcsr address in t0.

Comparing float value using memcmp because float value cannot be
directly compared for equality.

Put LOAD_REGISTER_FCSR and SAVE_REGISTER_FCC after LOAD_REGISTER_FLOAT.
Some float instructions may change fcsr register.