efi/gop: Get mode information outside the loop

Move extraction of the mode information parameters outside the loop to
find the gop, and eliminate some redundant variables.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200320020028.1936003-4-nivedita@alum.mit.edu


Signed-off-by: Ard Biesheuvel <ardb@kernel.org>