drm/i915: Simplify onion for bxt_ddi_phy_init()

drm/i915: Simplify onion for bxt_ddi_phy_init()

Older compilers (gcc-4.9) are not as able to track uninitialised
variables as well as more recent compilers. In particular,

drivers/gpu/drm/i915/intel_dpio_phy.c: In function ‘bxt_ddi_phy_init’:
drivers/gpu/drm/i915/intel_dpio_phy.c:482:25: warning: ‘was_enabled’ may be used uninitialized in this function [-Wmaybe-uninitialized]

In this case, we can rearrange code slightly to make the control flow
clearer to the reader, as well as the compiler. That is we only call
uninit using the same predicate as calling init

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171107135324.28300-1-chris@chris-wilson.co.uk
Reviewed-by: Gabriel Krisman Bertazi <krisman@collabora.co.uk>