target-mips: Stop using uint_fast*_t types in r4k_tlb_t struct

target-mips: Stop using uint_fast*_t types in r4k_tlb_t struct

The r4k_tlb_t structure uses the uint_fast*_t types. Most of these
uses are in bitfields and are thus pointless, because the bitfield
itself specifies the width of the type; just use 'unsigned int'
instead. (On glibc uint_fast16_t is defined as either 32 or 64 bits,
so we know the code is not reliant on it being exactly 16 bits.)
There is also one use of uint_fast8_t, which we replace with uint8_t,
because both are exactly 8 bits on glibc and this is the only
place outside the softfloat code which uses an int_fast*_t type.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>