tpm: fix the return code, if the eventlog buffer is full

We currently return 'No space left on device' if the eventlong buffer
we allocated is not enough. On a similar check later on that function
during the call to tcg2_log_init() we return 'No buffer space
available'. So switch both error codes to -ENOBUFS since we are always
checking a buffer and not a device.

Fixes: commit 97707f12 ("tpm: Support boot measurements")
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>