Instead of re-reading, masking and endianness correcting the same trb
several times to get the trb type from an event, just do it once and
store it in a local variable.

Also pass the trb_type directly to the vendor specific event handler,
avoiding one more similar read.

In addition to the security benefit this also cleans up the code
and helps readability.
Signed-off-by: NMathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20210129130044.206855-13-mathias.nyman@linux.intel.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>