arm: vfp: Bounce undefined instructions in vectored mode

Certain ARM CPU implementations may not raise a floating-
point exception whenever deprecated short-vector VFP
instructions are executed. Change the VFP exception
handling code to emulate short-vector instructions even
if FPEXC exception bits are not set.

Change-Id: I2443d09a92c8947343126a3b6c2a074af1a62057
Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>