net: mvpp2: ptp: Fix unused variables

In the functions mvpp2_isr_handle_xlg() and
mvpp2_isr_handle_gmac_internal(), the bool variable link is assigned a
true value in the case that a given bit of val is set. However, if the
bit is unset, no value is assigned to link and it is then passed to
mvpp2_isr_handle_link() without being initialised. Fix by assigning to
link the value of the bit test.

Build-tested on x86.

Fixes: 36cfd3a6 ("net: mvpp2: restructure "link status" interrupt handling")
Signed-off-by: Alex Dewar <alex.dewar90@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>