net: ipa: a few simple renames

The return value of gsi_command() is true if successful or false if
we time out waiting for a completion interrupt.

Rename the variables in the three callers of gsi_command() to be
"timeout", to make it more obvious that's the only reason for
failure.

In addition, add a "gsi_" prefix to evt_ring_command() so its name
is consistent with the convention used for GSI channel and generic
commands.

Signed-off-by: Alex Elder <elder@linaro.org>
Reviewed-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>