KVM: arm64: Fix table format for PTP documentation

The documentation build legitimately screams about the PTP
documentation table being misformated.

Fix it by adjusting the table width guides.
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Marc Zyngier <maz@kernel.org>

Documentation/virt/kvm/arm/ptp_kvm.rst

@@ -12,7 +12,7 @@ host to the guest using a KVM-specific hypercall.
 This hypercall uses the SMC32/HVC32 calling convention:
 
 ARM_SMCCC_HYP_KVM_PTP_FUNC_ID
-    =============    ==========    ==========
+    ==============    ========    =====================================
     Function ID:      (uint32)    0x86000001
     Arguments:        (uint32)    KVM_PTP_VIRT_COUNTER(0)
                                   KVM_PTP_PHYS_COUNTER(1)
@@ -22,4 +22,4 @@ ARM_SMCCC_HYP_KVM_PTP_FUNC_ID
                       (uint32)    Upper 32 bits of counter (r2)
                       (uint32)    Lower 32 bits of counter (r3)
     Endianness:                   No Restrictions.
-    =============    ==========    ==========
+    ==============    ========    =====================================