bcm2708_fb: remove unnecessary initialization of result

static analysis by cppcheck detected an unnecessary initialization
of variable 'result' which is re-assigned almost immediately after
the initialization.  Remove the redundant initialization.

[drivers/video/fbdev/bcm2708_fb.c:406]: (performance) Variable
  'result' is reassigned a value before the old one has been used.

Signed-off-by: Colin Ian King <colin.king@canonical.com>