In order to compare data read from the target with some marcros or data
defined on the host, we must transform this read data from target
endianess to host endianess.
target_read_memory() gets bytes from target to the host, but keeps them in _target_
endianess. This is OK if we just want to temporary keep this data on the
host, like keeping breakpoint->orig_instr. But if we want to use this
data for any ispections and comparisons on the host side, we must
transform it to _host_ endianess, by using target_buffer_get_u32()
function.
Currently this transformation is missing, and check current_instr ==
MIPS32_SDBBP will never pass if target and host endianess differ,
because current_instr will be kept in _target_ endianess and
MIPS32_SDBBP will be kept in _host_ endianess,

The patch fix this issue by using target_buffer_get_u32() to transform current_instr to
_host_ endianess before comparison.