efi_loader: fix EFI_ENTRY point on get_active_pcr_banks

efi_tcg2_get_active_pcr_banks doesn't immediately call the
EFI_ENTRY() wrapper once it enters the function. Move the call a
few lines above to cover the error cases properly as well.

Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>