forked from Mirrors/opensbi

As per the current SBI specification, sbi_getc should return an int instead of char. In case of FIFO is empty, return -1 as per the specification. Reported-by: Sergi Granell <xerpi.g.12@gmail.com> Suggested-by:Thadeu Lima de Souza Cascardo <cascardo@cascardo.eti.br> Signed-off-by: Atish Patra <atish.patra@wdc.com>