ANDROID: KVM: Fix func filter HVC for pKVM Ftrace

The function hyp_ftrace_sync() is meant to apply the filtering described
by the host provided func page to an array going from funcs to
funcs_end. The end parameter is optional and must defaults to the upper
boundary of the ELF section __hyp_patchable_function_entries. The start
however is required and a value (most likely the return value for
hyp_ftrace_find_host_func()) must be given. Therefore, do not override
the start parameter when the optional end one isn't given.

This fixes cases where some functions were not properly
enabled/disabled.

Bug: 411075717
Bug: 357781595
Fix: e630ddc2 ("ANDROID: KVM: arm64: HVCs to filter Ftrace for pKVM hyp")
Change-Id: Ic9094c9de0599c8249ad1d7961e390c726c1208a
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>