arm64: KVM: Fix architecturally invalid reset value for FPEXC32_EL2

Due to what looks like a typo dating back to the original addition
of FPEXC32_EL2 handling, KVM currently initialises this register to
an architecturally invalid value.

As a result, the VECITR field (RES1) in bits [10:8] is initialised
with 0, and the two reserved (RES0) bits [6:5] are initialised with
1.  (In the Common VFP Subarchitecture as specified by ARMv7-A,
these two bits were IMP DEF.  ARMv8-A removes them.)

This patch changes the reset value from 0x70 to 0x700, which
reflects the architectural constraints and is presumably what was
originally intended.

Cc: <stable@vger.kernel.org> # 4.12.x-
Cc: Christoffer Dall <christoffer.dall@arm.com>
Fixes: 62a89c44

 ("arm64: KVM: 32bit handling of coprocessor traps")
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>