display_bootlogo in nlaunch.c fails to compile

[fb39ca4]

I have been using arm-none-eabi-gcc 7.2.0 to compile nLaunchy.

In the function display_bootlogo there are several errors:

• There is a semicolon after the if statement, making its code always run instead of only when the file was opened successfully. GCC warns about this, and the makefile has GCC treat it as an error.

• buffer_size is undefined

• The pointer to the screen buffer is not cast to the correct type which causes warnings that become errors. I'm thinking it should be *(unsigned* volatile*)0xC0000010 instead of *(volatile unsigned*)0xC0000010.

[nunopenim]

For nlaunchy I always use gcc 7.0, newer than that never really worked for me. That feature was from a nlaunchy 2.3 variant, if I am not mistaken.