mips: mips32_pracc_fastdata_xfer() little modification

In this function after loading the handler code and the jump code there is a call
to wait_for_pracc_rw() to verify that a pracc access is pending.
Next the address is read to verify that the handler is running, the address should be at
fastdata area.
Next, another call is made to wait_for_pracc_rw(). This call is not needed, we now already
that a pracc access is pending.
Better we call this function before loading the end address to be sure it is loaded correctly.

Signed-off-by: Salvador Arroyo <sarroyofdez@yahoo.es>
Change-Id: If311450ea634786fc28cf1a8e18ed24ce5257d20
Reviewed-on: http://openocd.zylin.com/1142
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>