To support FRAME_POINTER avoid using a7 in __simc (none of the existing
simcalls needs it). Replace calls to __simc with more specific
simc_read, simc_write and simc_lseek calls.
Signed-off-by: NMax Filippov <jcmvbkbc@gmail.com>
Signed-off-by: NChris Zankel <chris@zankel.net>