soc: qcom: ipa: kill ipa_sram_settings_get()

Incorporate what ipa_sram_settings_get() does into the top of
ipa_smem_init() and get rid of ipa_sram_settings_get().  Remove
ipa_sram_settings_clear() as well.  Change the return value if the
size available isn't big enough for the sizes assumed by the code,
to distinguish this from being unable to map the memory.

Signed-off-by: Alex Elder <elder@linaro.org>