aarch32: Fix multiple bugs in amu_helpers.S

AArch32 uses odd-even pairs when passing 64-bit arguments to
functions.  For example in `amu_group0_cnt_write_internal()` the
second argument is a uint64_t which is passed in r2 and r3.

In `amu_group1_set_evtype_internal()` the value that needs to be
written to the system register is in r1 not in r0.

Change-Id: I20196268fdb1dc9ef6c4ebe61e761fba9623b3f2
Signed-off-by: Dimitris Papastamos <dimitris.papastamos@arm.com>