hw/drivers/spiram: Fix build warning for non bus driver build
hw/drivers/spiram: Fix build warning for non bus driver build

label end was used only in bus driver build.
goto is now removed and ifs are used instead.

mlaz/mynewt-core,mlaz/mynewt-core,mlaz/mynewt-core,mlaz/mynewt-core,mlaz/mynewt-core