firmware: qcom: Fix hyp_log issue

While reading the hyp logs few garbage characters were seen
due to invalid len computed. This patch fixes the issue by
properly computing the len.

Change-Id: I2e2f23d069ee45b0c57a7b673248b63eedaf7697
Signed-off-by: AnilKumar Chimata <anilc@codeaurora.org>