target/mips: Replace GET_LMASK64() macro by get_lmask(64) function

target/mips: Replace GET_LMASK64() macro by get_lmask(64) function

The target endianess information is stored in the BigEndian
bit of the Config0 register in CP0.

Replace the GET_LMASK() macro by an inlined get_lmask() function,
passing CPUMIPSState and the word size as argument.

We can remove another use of the TARGET_WORDS_BIGENDIAN definition.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20210818215517.2560994-4-f4bug@amsat.org>